Having removed Internet Explorer 8 from a Citrix Presentation Server farm, the following errors started appearing in the Application Log:

IE8 uninstall errors in App. Log (1)
It shows up with 2 different messages, but with the same event ID:

IE8 uninstall errors in App. Log (2)
.. and

IE8 uninstall errors in App. Log (3)
This happens because IE8 doesn’t remove all traces when it uninstalls. There’s 2 leftover (empty) keys in the registry, and the errors then appear everytime a user is accessing IE7.
The keys to delete are:
7B849a69-220F-451E-B3FE-2CB811AF94AE
CF7639F3-ABA2-41DB-97F2-81E2C5DBFC5D
And they are both found in:
HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\GPExtensions\
Apparently this error has been present since IE8 beta, and it still hasn’t been fixed by Microsoft. Shame on you.
No restart needed.
#1 by dhalsin on November 5, 2009 - 21:27
Thank you!
After I deleted the 2 keys the problem was solved.