I had Internet Explorer crash twice on Vista today. The first time I had several open windows die and they could not be closed. I had to reboot to get everything back to normal. I went in to advanced options and changed IE to open each new window in a new process and continued. The second time things got very strange...
At first all instances of IE closed. I then saw a dialog window on top of all other windows but this dialog, titled "Microsoft Windows", was empty of any normal dialog text and completely transparent. I could see right through it! I could not close it either with the red X in the top right corner or by selecting close from the task bar right-cllick menu.

Furthermore my CPU usage went high with Explorer.exe pegged at 50%. There was also a second copy of Explorer.exe at 0% which I hadn't seen before. On a hunch I selected the window and did a Ctrl-A, Ctrl-C and attempted to paste the result into Notepad and this is what I got:-
[Window Title]
Microsoft Windows
[Main Instruction]
Internet Explorer is restarting...
[Content]
Windows is checking for a solution to the problem...
[Cancel]
Killing both copies of windows explorer did not help but ending a process called "WerFault.exe" made the dialog go away. I guess this is a Vista bug of some kind and might be worth reporting if it erver happens again:-(
Cheers,
Neale