This page runs through some of the most common problems you might have when trying to use the interactive modellers available on the USS website. If you are unsure why the modeller is not working, read through this page in order to try and diagnose the problem.
Java modellers can be embedded into web pages as an 'applet' to provide functionality that may not be possible with other technologies. In order for a Java applet to work, a user must have a Java Virtual Machine (JVM) installed. A JVM is bundled either with the user's operating system or web browsing software and is installed and enabled by default.
Flash modellers can also be embedded into web pages, but require the user to install a Flash player. This is usually included in the user's browser but will not be installed by default on any handheld device.
In most cases, the loading and the subsequent running of the modellers is completely automatic and the modeller simply appears as part of the requested web page.
However, due to the wide variety of operating systems and web browsing software available and being used, some problems are inevitable. The rest of this page aims to explain and provide solutions for most of the known problems with using the modellers.
Common problems and solutions
Before trying to diagnose any modeller problem, it is recommended you do the following:
- open the modeller in your browser window
- with the window in focus, press CTRL+F5 (Windows users) or APPLE+R (Mac users). This will ensure the latest files for the modeller are downloaded from the webserver.
If there is a specific problem that can be identified from the list below, simply scroll down for an explanation of how the issue can be solved. Please read the problem descriptions carefully as many problems can share the same symptoms.
Different modellers use different technologies, therefore not all these solutions will apply to all modellers.
- Flash not installed
- Request to install 'Microsoft virtual machine' plug-in
- 'java.lang.classnotfound' or other Java error
- Security warning pop-up
- Blank grey box instead of the modeller
- Blank page instead of modeller.
1. Flash not installed/up to date
When accessing a Flash modeller you receive a warning message that Flash is not installed or is not up to date. These modellers require the Flash plug-in to be installed in order for calculations to take place.
Unfortunately Flash is not available on most mobile devices and these Flash modellers will only work on PCs or Macs. Flash can be installed by visiting www.adobe.com/support/flashplayer/downloads.html
2. Java Virtual Machine (JVM) not installed
Some operating systems do not come with a JVM installed.
Not having a JVM installed will cause some of the modellers to fail:
- If you are running Internet Explorer and have 'Install on Demand' enabled (which is the default option) you should receive a prompt asking whether you wish to install the 'Microsoft Virtual Machine' when trying to access a modeller.
- If you are unsure whether you have 'Install on Demand' enabled or a 'JVM' installed you should check in your Internet options dialog under Advanced options.
- If a JVM is installed there will be a sub-section titled Microsoft VM or Java (Sun).
- If you are running another browser, you can check for the presence of an installed JVM by clicking Help/About Plug-ins. If 'Java plug-in' is listed then the user already has a JVM installed.
You can install Java by visiting: www.oracle.com/technetwork/java/javase/downloads/jre7-downloads-1880261.html
3. Java errors
You may experience java.lang or other Java errors. This problem could have several causes:
- Due to the personal nature of some of the information entered into some of the more advanced modellers, the data is encrypted when it is sent to the web server. In order to guarantee the validity of this encryption USS has been issued with a security certificate.
- When using Java it is necessary to manually accept the security certificate, by means of a dialog box, in order for the modeller to be able to communicate with the server.
- If you reject the security certificate the modeller will fail and an error may be reported in the status bar or the Java console
- Other Java errors may be caused by corrupt or very old implementations of the JVM being installed on the client machine.
The solutions to these problems are outlined below:
- The security certificate induced errors can be solved simply by accepting the security certificate when requested.
- Errors caused by corrupt or out-dated installations of the JVM can be corrected by downloading and installing the latest version of a JVM. Instructions on how to do this are available in the 'Java virtual machine not installed' solution above.
4. Java not enabled
You may find that running a modeller brings up an empty window (some modeller windows may contain 'print' and/or 'back' buttons at the bottom, with a blank space above them). This happens when the JVM has been disabled in the browser's preferences.
Providing you have a JVM installed, it can be enabled by opening your browser's tools/preferences menu. In the application/extensions there is the facility to enable Java.
5. Custom security settings
If you are using Internet Explorer and the default security settings have been modified, it is possible that this could prevent Java applets from running. If the security settings have changed then Internet Explorer users may receive a security warning such as 'Your current security settings prohibit running ActiveX controls on this page. As a result, the page may not display correctly' when trying to access a modeller. This warning can also appear if you do not have a JVM installed and also have 'Install on Demand' disabled. You should read the 'Java virtual machine installed' section to make sure this is not the case.
In order to give permission for Java applets to run you need to alter your Internet Explorer security settings. To do this you must go into the Tools menu and select Internet options.
From here you need to select the Security tab then select the Internet zone and click on Custom settings. You need to scroll down the list until you come to the section labelled Microsoft VM. You will need to select High safety under Java permissions.
6. Java Runtime/virtual machine (VM) out of date
A grey box is observed where the modeller would be expected to appear. This is usually a sign that an out of date, unsupported virtual machine (sometimes referred to as the Java plug-in, or Java Runtime Environment) is installed.
Please download and install the latest version of Java.
If you are unable to diagnose and/or solve your specific problem you can request further support by emailing the webmaster.
The more information you provide about your specific problem the easier it will be to try and find a solution.
If possible, please include:
- the modeller you were trying to use
- the exact problem you have encountered
- any error messages received
- the operating system you are using e.g. Windows XP/Vista/7/8, Mac OS X, UNIX etc
- the make and version number of your web browser e.g. Internet Explorer 7, Chrome 32 etc