I've never got that update warning, and I was running on 3.58 up till few days back. However, before I've updated FF to 3.6 I've experienced problems with scrolling, loading of video etc. Now it works perfectly. No more crashing on flash sites etc.
Try this.
Go to:
http://www.macromedia.com/support/docum ... ger06.html and
Delete all sites.
Also, make sure to delete all browsing history, cookies etc. Running a CCleaner's Registry integrity check might help. Fix all issues but make sure to backup it before.
http://www.ccleaner.com/
*Hopefully, Ciro will skip this topic without posting a novel about Opera's superiority