You can see the flash version and revision you're using at this page:
http://www.adobe.com/software/flash/about/If you see in the rectangle "Version Information" the line:
"You have version 10,1,82,76"which is the latest revision of version 10.1 of Flash Player,
then you will experience the issue of the scrollbar going back to top.
This problem is not related to windows or Explorer
as I run a Linux Fedora 12 firefox and version 10.1 revision r82.76
exhibits this problem too on this plateform.
No need to go back to Flash 9 or even Flash 10.0 to fix the issue.
Reverting to the older revision r53.64 of Version 10.1 will solve the problem.
The older versions/revision are archived here:
http://kb2.adobe.com/cps/142/tn_14266.htmlDownload archive of Flash Player 10.1, unzip it.
It contains all revisions of version 10.1 for multiple plateforms.
Select the version/revision 10_1r53_64 for your plateform.
For Windows users, this should be the directories and file:
fp10.1_archive/10_1r53_64/flashplayer10_1r53_64_win.exeInstall it, restart your browser.
Check again the new version is installed at the page:
http://www.adobe.com/software/flash/about/You should see:
"You have version 10,1,53,64"Scrollbar of chatbox should work normally with this revision.