1.
Instead of left clicking on the "Launch NetLab" link, right click and select "Save Target As...", and save the JNLP file to a known location, such as your desktop. You can then launch the application by double-clicking this file.
Note that this JNLP file is not the entire application, it is a very small text file (less than 1kB) that is used to by Java WebStart to download and install the application seperately, so don't be suprised by the quick download. When you have launched the application once, you can safely delete the JNLP file and use the NetLab shortcut in your system menu (eg. Start -> Programs -> UniSA -> NetLab) to launch the application in the future.
2.
Clear your cache by deleting your Temporary Internet Files. To do this, select the Tools menu in Internet Explorer and select "Internet Options...". In the General tab, under "Temporary Internet Files", click Delete Files, and click OK. But be warned, this may take several minutes.
Note: Don't worry, this wont delete anything important. It merely deletes images and HTML files from web pages that you have visited in the past that your browser stored when it displayed the pages.
3.
Use or as your browser instead!