[CentOS] Flash plugin not working

Hi,

I have a fresh install of CentOS 5.5, with a minimal GNOME desktop. I 
configured RPMForge as third party repo.

I updated everything first, then installed flash-plugin. (And yes, I 
restarted Firefox... :oD). All I see when I try to see some things Flash 
on the Internet, like Youtube or the likes, I get... nothing. The space 
remains white. Sometimes a black square will appear, sometimes it will 
redisappear again.

$ rpm -q flash-plugin
flash-plugin-10.1.82.76-0.1.el5.rf

I also tried to give the more recent version from Adobe a shot, with the 
same result. I took a look in /usr/lib/mozilla/plugins, where everything 
seems normal.

$ ls -l /usr/lib/mozilla/plugins/
total 0
lrwxrwxrwx 1 root root 39 nov  8 22:22 libflashplayer.so -> 
/usr/lib/flash-plugin/libflashplayer.so

Which leaves me clueless. Any suggestions ?

Cheers,

Niki