finally works for me - it was all about the sd card

so here's my setup and tests:
SanDisk 8GB SD Card Class 4
ViperGC + SDLoad Plugin -> Swiss 0.1R24
all were loaded via Slot B WiiKey SD adapter with video settings set to Auto
Compatible Mode:
Ikaruga NTSC - slightly hangs some time......totally playable though
Mario Party 7 PAL - very slightly sound problems
Baten Kaitos PAL - green screen, loads after 3 secs. sound/video hangs every 2 minutes...
Conflict Desert Storm NTSC - green screen
Hitman 2 NTSC - green screen
Fast Mode:
Ikaruga NTSC - sound glitches
Mario Party 7 PAL - very slightly sound problems
Baten Kaitos PAL - green screen, loads after 3 secs. sound/video hangs every 2 minutes...
Conflict Desert Storm NTSC - green screen
Hitman 2 - green screen