I haven't. I wound up with a nasty Synaptic Package Manager corruption that took a while to fix. Link below...
If you've been able to get flash to work in firefox 3.5.5, could you please tell me how? Thanx...
Package Manager fix....
The symptom was that whenever I tried to run the Package Manager, I got an error that said something about "flash player needs to be installed, but there's no archive."
The fix is at this link...
http://ubuntuforums.org/showthread.php?t=1305829&page=3
Scroll down to #23, and read the corrections in the posts following.
Comment: I believe there's a misplaced Save/Close in the procedure. I assumed that it should be beyond that big block of quoted text & that made it work. It was good to have the Package Manager back!
Good luck.