Oh bother...something else is blocking it then. I do remember having a bit of trouble installing gcc-4.5 on my system but I didn't keep record of exactly how I did it.
In the meantime, until I think of something else to try, you could try installing the 2.6.31-rt kernel from the AVLinux ftp:http://www.bandshed.net/kernels/126.96.36.199-rt21-rev4-PAE.zip
It's an old kernel I know, but it was an awfully good kernel. You may need to run sgfxi and install the NVidia binary drivers to get your graphics card working well on this kernel.
Sorry it is taking so long to help you resolve this...