Fedora xen - Feb 2007 - Failed to obtain physical IRQ

Hi,

I tried to boot a FC6 domU with kernel 2.6.19-1.2911.fc6xen. When I try 
to activate the network device (physical NIC, hidden from dom0)

    ifconfig eth0 up

I get this error msg:

   Failed to obtain physical IRQ 10
   eth0: link up, 100Mbps, full-duplex, lpa 0x45E1

ifconfig says, the device is up but pinging another host doesn''t work.
I
tried to change the pci-slots, the NICs and used different drivers, the 
error message remains (just the IRQ changes). It seems that this is not 
a hardware problem.
Googling the error message didn''t help much. What can do to narrow down
the problem?

Thanks, Chris