I have put a new gpc snapshot at:
http://www.math.uni.wroc.pl/~hebisch/gpc-20060325.tar.bz2
Main change is preliminary gcc-4.0.x support. The other changes are rather small. Note that for "production use" 3.4.x and 3.3.x backend are prefered. Also, using 2.8.1, 2.95.3 and 3.2.3 backend should work, but is depreciated.
For more detail see:
http://www.math.uni.wroc.pl/~hebisch/gpc/NEWS-20060325
and
http://www.math.uni.wroc.pl/~hebisch/gpc/Fixed-20060325