Blender Crashes with audio in sequencer or Png sequence in background image

Hi there,
I’ve had the sampe problem with 2.48 on a windows machine. Now I’m on a Mac with 2.49 and 2.49a. I’m running OSX 10.5.7 with 8Go of RAM.
Everytime I load a sequence (png, jpeg, tga or even some Quicktimes) in the background image panel in a 3D viewport, blender seems to handle it for a while and then it crashes.

From the terminal :

Compiled with Python version 2.5.1.
Checking for installed Python… got it!
Mapalloc returns nill, fallback to regular malloc: len=6220800 in imb_addrectImBuf, total 3160056720
blender(354,0xa0646720) malloc: *** mmap(size=6221824) failed (error code=12)
*** error: can’t allocate region
*** set a breakpoint in malloc_error_break to debug
Calloc returns nill: len=6220800 in imb_addrectImBuf, total 3175812052
Bus error

It seems there is a problem allocating Ram. But the .png sequence or the Wave file are quit small (almost 2,5 Go for all). I had the exact same problem on different OS and computers since I use blender (for 3 years now). I’ve just tested my ram with memtest for mac and it seems there is no problem…
So what am I doing wrong ?
Do I need to set something in the blender preferences tab ?
Thanks for your time ! :smiley: