multiple links in backbutton using msie6 on asp.net site

Here's the prob...
This occurs *only* with clients on Windows XP SP2 using MSIE6.x .. all other browser & o/s conbinations work fine.

Have an ASP.net website, pretty typical site, some assemblies, sql server db on a Win2K server.

When the user visits the site with MSIE6.x, clicks thru the various links and menus to navigate the site, each page they visit generates multiple listings in the back button history.

So go from page A.aspx to page C.aspx, there will be about 5 links in the back buttons dropdown.
And to get back to A.aspx, you have to click back about 5 times.

Code problem? - i think not, no other browser is affected
Windows XP sp2 problem? - probably, sp1 NOT affected
Or MSIE the culprit? - a setting?

I've already wasted an hour of my life on the phone with MS support. Now it's time to consult with the real experts.

Suggestions or advice would be appreciated.