I’d like to take this time to point out that Realplayer 11 is a piece of garbage, shitware of the worst sort. The Mac version is almost completely non-functional; the Windows version isn’t much better.
And Realnetworks makes it hard to find the older versions, the bastards. If you need to use RealPlayer for any reason, I highly recommend you downgrade to version 10, available here for Windows and here for Macs. I very rarely watch movies on my linux machines, but would guess that compiling an MPlayer would be a better way to go. The last version of Realplayer for linux wasn’t too impressive.