Could be a sign of spyware/virus,have you run any scans?
Try running AVG ANTI SPYWARE and your AV in safe mode.
Sometimes cleaning cookies helps,after scanning try CCLEANER.I use the slim build.
Have you considered a different browser like FIRE FOX
Tom
Everytime I try to logon to Chase.com, I get the following: internet explorer has encountered a problem and needs to close. We are sorry for the inconvenience. Error Signature: appname: iexplore.exe, modver: 5.1.2600.3119, appver: 7.0.600.16473, offset: 00012a5b, modname: kernel32.dll. I am running windows xp, sp2 and ie 7.0. This only happens to one website. Jerry

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