I had posted a message in a Security branch of TechNet's newsgroup but have had 0 response so I thought I'd try here

I recently found identical symptoms on two PC's.  One is a home PC that sits behind an out-of-the box router (the firmware was upgraded) and has Norton Internet Security for firewall and virus protection (lots of spyware on this PC!)  The other is on an employee's PC that has Symantec Corporate Antivirus and our corporate firewall(s) and policies protecting it (no spyware found on this PC).  Both had Virus definitions and Windows security updates all up-to-date.  Both machines are Windows 2000 PC's with IE6 and MSN installed.  No malicious symptoms (open ports, unknown processes or services running, obvious registry changes) were noted on either PC

The weird symptoms are
1) The "Delete Cookies" button on the General tab in the Internet Options tool is missing
2) There is a blank "Miscellaneous" entry in the Security Settings screen you get when editing the Custom Level settings for the Internet zone on the Security tab in the Internet Options tool.  This blank entry has two radio buttons checked on (prompt and disable).  (There are other blank entries in other settings pages found but this is the first I noticed.
3) The Help -> About Internet Explorer page shows the IE5.5 logo and yet shows the version to be 6.0

Both PC's were being looked at for different issues.  The home PC had spoolsvc continuously shut down when restarted.  The employee's PC entered into a continuous reboot cycle after a reboot (rebooting itself shortly before reaching the Login screen--the reboot issue was resolved with a W2K OS repair)

Suspecting a W2K SP4/IE6/April 13 updates problem, we rolled back the Apr 13 Security updates on the work machine but the problem persisted.  An IE6 repair failed (not sure what err msgs) and IE6 uninstall/reinstall cleared the above symptoms but netted Windows startup err msgs like:  "winlogon.exe - Entry Point Not Found : The procedure entry point SaferSetLevelInformation could not be located in the dynamic link library ADVAPI32.dll."  (And the same msg with shmgrate.exe, Synchronization Manager:mobsync.exe, Symantec AntiVirus Corporate Edition:vptray.exe, and WMS Spooler:MAPISP32.exe entry points not found in ADVAPI32.dll.

Any insight anyone could offer would be greatly appreciated!