I'm not able to use Flash Player in Windows 7 64bit Guest Account, while i can use it with other Administrator or Standard accounts. I have already tried to unistall flash player following your guide at http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html
If i open http://www.adobe.com/software/flash/about/ with the Guest Account i can not see my version information, but if i do the same with any other account i can read You have version 11,2,202,235 installed.
It happens both with IE9 32bit and 64bit.
I suspect we're running into a permissions issue here. You could try running through the steps listed in this FAQ. I'll also ping our install team to see if they've done any guest account testing.