Hello! My name is Sergey. I'm from Russia. Sorry for my bad English.
My configuration:
Windows XP pro SP3.
SEP 12.1.
Internet Explorer 8.
I had the same problem. What I did:
1. Reinstalled SEP 12.1. - did not help.
2. Installed update "RU1" - did not help.
3. Used utility "CleanWipe" for the complete removal of the SEP 12.1. Then installed again SEP 12.1. Didn't help.
4. Use the Microsoft Windows Update to install the latest updates for Windows XP pro SP3. Didn't help.
5. Provide a group of users "All" full rights for the folder "C:\Documents and Settings\All Users\Application Data\Symantec\Symantec Endpoint Protection\12.1.1000.157.105\Data\LUE" and its subfolders. This was done in "Safe mode". Didn't help.
I read the forums on the site "symantec.com" and found that many of the problems associated with Internet Explorer. Then I decided to uninstall Internet Explorer 8 and return to Internet Explorer 6.
After a reboot the problem with the "SEP 12.1" decided.
But this is not a solution. It is a contravention of the problem. Not everyone can remove Internet Explorer 8, because on some systems it is integrated into the Windows.
And now a question to the technical support Symantec: what the settings should be done in Internet Explorer 8, to SEP 12.1 worked correctly?
Faced the problem for thousands of users, but a proper solutions so and not found...