[Fedora-xen] PAE kernels not working but non-PAE does

[Jason Tower]

i have several dell poweredge 2650s with 4gb ram (these are 32 bit
xeon cpus) running fc5 w/ the 2.6.17-1.2174_FC5xen0 kernel, the domUs
are ubuntu dapper images booting the 2.6.17-1.2174_FC5xenU kernel.
everything works beautifully, very stable.

i was hoping to squeeze some more domUs on these systems by adding
additonal ram and using the PAE kernels.  unfortunately booting
2.6.17-1.2174_FC5xen in the dom0 breaks networking (the bridges are no
longer created) and the domU won't boot at all (kernel panic, can't
find /dev/sda).  i've also tried the latest fc5 kernel and the stock
fc6 kernel and get the same result.  i've copied
lib/modules/2.6.17-1.2174_FC5xen to the domU's root filesystem and am
using the matching initrd but no joy.

is it possible to make this arrangement work?