IE6 SP2 - Problem logging into a secure website

[pequod-ge]

Hello, I have a situation where users on one computer running WinXP2 with IE SP2 cannot login to a secure website. It worked a few weeks ago, but about 2 weeks ago, it stopped working. It seems to be unique to this one computer when accessing this one site. Other similarly configured computers at this site have no problems. What we experience is:

o Get login page
o enter username/password
o click the login button
o Watch progress bar go across all the way
---- page detail goes blank
---- address window momentarily presents url with "sslredirect" embedded string
---- bottom line flashes something about 128-bit encryption
o Watch progress bar progress 2nd time --- to about 1/2 way
o Login page presented again - no error messages in the page or in the status line
o Try to login again / more of the same - it's a tight loop

We've tried
o disabling all add-ons
o using hijackthis to identify unwanted add-ons and other crimes - all removed
o separate virus scan (using symantec corp ed AV (aka Client Security) V 10.1
o deleting all offline content
o deleting all cookies
o clearing the ssl cache and userid/passwords
o creating new user and new profile

NONE of these actions helped. Still can't get past the login.

We also note that we can login to other secure sites without problems.

Any suggestions short of brute force FDISK recovery or re-installing / repairing WinXP SP2 or running SFC/Scannow??

Thx.