I've tried on a number of different machines to re-create your issue (which I believe to be a Java related plug in - like most forum sites use).........I can't. I haven't gotten a prompt for a plug-in download on either of the 3 laptops, nor on my company or home networks.
So, you may want to make a note of the version of IE/Safari/Chrome/or Mozilla browser you are using. Can you upgrade or try on a different browser.
You can also look at your active plug-ins before and after you download, to identify what it is.
Worst case scenario - you'll have to use a PC that does not infringe on your Server security. i.e. laptop at a coffee shop
Hope this helps.
Regards