Stepmania crashes (BG Animations?)

[dakilla]

hello i have got a problem that i cant find any solution to.. so now i am asking for some help..

nearly everything works fine..
when i am starting stepmania this warning comes:

Couldn't load driver ALSA: Not enough substreams for hardware mixing, using software mixing
ALSA: Software mixing at 44100hz
Sound driver: ALSA-sw
/////////////////////////////////////////
WARNING: Unknown lights driver name:
/////////////////////////////////////////
but the sound works greate and all..
and i have animated characters that works fine..
but when i try to run a song with video as BG it crashes...
and this displayes

ptrace failed: Operation not permitted
ptrace failed: Operation not permitted
ptrace failed: Operation not permitted

and in the "/tmp/crashinfo.txt" the only error i can find is:

Thread: Main thread
../../src/RageSurface_Load_PNG.cpp:42
../../src/RageSurface_Load_PNG.cpp:42
../../src/RageSurface_Load_PNG.cpp:42
../../src/RageTextureManager.cpp:108 RageTextureManager::LoadTexture(Songs/DDR Anime 1st Mix/Chobits/ChobitsIntro.avi). ../../src/arch/MovieTexture/MovieTexture.cpp:86 Assertion 'DriversToTry.size() != 0' failed

plz help me!