I had one of my users come and grab me saying that their Internet wasn't working. Anyone who has worked long enough with computers knows this can mean anything but since I was just using the Internet to pull up some information, so I knew it wasn't building wide.
I followed her to her desk and she launched Internet Explorer 8. It opened and then instantly closed itself. Odd, I opened my self and it did the same thing but stayed open a little longer. I popped open task manger to ensure nothing funny was happening. Didn't see anything funny. I jumped into "Internet Options" and changed the home page to http://www.google.com/ since it is really basic and I thought maybe a page was causing the problem.
Opened IE again and this time it would stay open but the one tab kept crashing and the recovering the tab over and over again. I went ahead and went the through the same process as above and changed it to a blank page then reopened IE. Same behavior.
I thought maybe it was possibly malware behavior but wasn't really sure. Fired up Process Explorer and Process Monitor by Sysinternals. Process Monitor didn't seem to show anything odd. I then went to Process Explorer thinking that now it was probably a dll loaded with IE with causing a problem. Went to properties, and then Threads for iexplorer. I noticed one of the dlls that was pretty active was yt.dll. I looked at the top of IE and noticed a toolbar, after searching to confirm my thoughts the dll belonged to the yahoo toolbar. I uninstalled the tool bar and reopened IE. It was working fine.
Not sure what changed that caused the sudden problem, no updates happened in that time frame but if you start to have the same problem hope this helps.
UPDATE - I am seeing alot of traffic on this post and from the comments we can tell it's happening to multiple people and it started today. I only had one user with the problem. I saw a yahoo question about this apparently with vista it will tell you that yahoo toolbar is the problem, which would have made the proble easier. My user had xp and it told me nothing other than crashing. I will be contacting yahoo, if they don't already know. Curious if it's a certain toolbar version.
UPDATE 2 - I did see that the following update got installed yesterday on the computer: KB2079403. You can read the following link by microsoft http://support.microsoft.com/kb/2079403 and it seems to apply to all versions of windows. Dark stated his had a similar issue but that he had no such updated, and the last update was 11/19. So furhter proof it's most likely not microsoft update.
Update 3 - It looks like probably the problem had to do with an older version of the toolbar. Most people don't update theirs. What caused it to break today is still a mystery.
FOR THOSE WANTING JUST THE FIX AND NOT THE STORY
-Just uninstall the Yahoo toolbar.
-Install the latest version of the toolbar if you still want it. (Latest version seems to be working)