i have the same problem, im using mac 10.6.8. and it says i need flashplayer install even tho i have it already installed. ITS REALLY ANNOYING!

Ditto on Mac 10.7. Later I'm gonna try uninstalling the extra browsers we have. Already tried uninstalling and reinstalling flash. I've also seen windows 7 user's complaining of this happening. I'm also pretty sure users say that youtube videos works normally. It seems to run fine in the browsers. And all flash content seems to be working fine as well. (I run Windows 7 myself and don't have this issue, the issue is on a friends mac.)

Even my iMac has the problem. I've tried all the solutions from the F2 menu, but nothing has worked. I really want to watch videos using this gamemode... :(

I am on a mac 10.8.4 ... With the new flash player it dosent suport steam... I don't think windows 8 has suport on steam either... im gonna try and go back a update just to get "other browsers" for mac

i downloaded adobe flash player, reinstalled it 2 times and it still says Adobe flash was not detected. I downloaded it for "other browers". i Restarted Garry's mod then restarted my computer (which didnt work). I have a Windows 7 computer.

I'm on a friend's computer where it isn't working. I suspect the issue is that Windows 8 has Flash built in...
Actually, it wasn't working on IE/Chrome until I enabled it specifically for that browser, so right now if she got FireFox it wouldn't work.
I know youtube can run off of HTML5, so maybe see if the other can too, and then run off HTML5 instead of Flash.

ME TOO!!! i have windows 7 and still ADOBE FLASH StILL NOT DEDECTED!!!!!!!!!

I'm just sitting here waiting for a solution for IMac....