Ok, cool. That's some encouragement, but there's probably some other difference that's the real culprit. Oh.. are you running the server with PAE or in 64-bit mode?
Non PAE, and non 64 bit. Shall I reduce the amount of RAM I have? It just came into my mind that Xensource has some info about my HW:
"HP ProLiant DL380 G4, 2 x 3.6 GHz XEON, 4 GB RAM. Xen must be given option mem=3583M at boot (at least for non-PAE). With 2 QLogic HBAs installed there are problems initializing PCI and dom0 crashes, you may have to pass Xen the option acpi=off at boot. Fedora Core 5 test 1 and SLES 10 BETA 3 have been used for both dom0 and domU."
Ivan