I followed lifehacker's guide to get a proper tripple boot working usin rEFIt.
I used the 32bit KDE bt5 live dvd and then used the installer.
At the last screen of the installer, I went to 'Advanced' and configured the bootloader to be on the same partition as BT5 itself (as instructed in LH's guide).

Situation is now:
sda1: EFI i guess
sda2: OSX
sda3: Windows 7 (inc MBR)
sda4: Backtrack 5 (inc GRUB)

When I boot BT5 it gets stuck somewhere in the initialisation process.
Same happens in recovery mode.

I think it's strange it works with the live dvd, but not with the install.
It's not a bootloader problem since the problem occurs when loading backtrack 5 itself.

Is there somehow a way to figure this out?
Any help is appreciated, thank you.