What happens during BaseSystem verification?

[benzene]

Hi there, i installed lots of times many Tigers on quite a bunch of different machines and was always,
after some trying able to spot the problems i got during installation.
But not with Leopard.
I am stuck on installation right with the first package to install and the apple installer doesn´t give me any clues
about what excactly the problem is.
It stops with an installation failure window stating that the Base Package failed to verify and thats all.
Installer log says much the same .
A file i/o error can´t be the reason the disc is okay and has been checked several times.
In some other forum i read that this problem can also occur on real macs when installing leopard because of the use of non apple compliant
ram chips, but this has not been proofed.
Am i the only one with this problem?