Quick notes for the general case.
I'm not a fan of Silverlight on principle (the idea of desktop-like web pages sends chills down my spine), but technology-wise, my impression (as a programmer and occasional user of it) is that it's more stable than, say, Flash. And Firefox is pretty good with disabling or dumping plug-ins, so of the things you could install, it's low on the worry list.
For the error boxes, you might have luck with just a CTRL-C to copy the text to the clipboard. It'll also catch what's rolled off the screen, which is nice. Sadly, I only found out about that recently, despite having worked with Windows since the Dark Ages.