Problems with IE6

[tgx]

When A particular user logs in with IE6, then logs out and tries
to log back in again I am seeing this error generated and all
page loading stops:

Line: 1005
Char: 3
Error: 'AjxHistoryMgr' is undefined
Code: 0

All MS patches are applied.

I should also mention if I clear the browser cache
the user can log in again, but it recurs as above on
logout/login.

[SchlingBlade]

Do they have any type of adblocking or other anti-scripting software installed? Third-party firewall or content filtering software?

[tgx]

Do they have any type of adblocking or other anti-scripting software installed? Third-party firewall or content filtering software?

No. There is not any of this software installed. These machines are vanilla
W2k Professional workstations with all of the latest MS updates.