VLC not playing full screen (using -f)

[mutsu]

Currently when I play an video (.iso file), the video doesn't maximize to the screen. (maybe 720x480 near the cursor on the screen)

I'm using gentoo (2.6.34-r12. Ran emerge -uavDN world, then emerge -eav system world and rebooted for good measure.), mythtv (0.24.1_p20110709), vlc (1.1.10), xorg-server (1.10.2)
Hardware:
AMD X6 1055T Processor
nVidia Corporation G92 [GeForce 9600 GSO] (rev a2)
Dual head 1920x1080 screens using twin view (I've tried using only one screen and changing the xorg.conf file, but it doesn't make a difference.)

I using the following command line from inside mythtv to play a .iso file (both .ISO and .iso have the same problem)

cvlc -f --video-on-top --spdif %s vlc://quit

I'm using 1.1.10
I've also tried using both the -width and -height flags to force the screen, but all it does is make the rest of the background black and put the video in the top left.

Every once in a while the video will play full screen. No control over when it does.

Any ideas?
(Additional information will be provided if needed)

[Rémi Denis-Courmont]

Uh, any window manager running?

[mutsu]

evilwm is the one being used. version 1.0.1.

[Rémi Denis-Courmont]

Check that you do have the XCB output plugins available, the XCB window plugin, and that the WM supports EWMH fullscreen mode.