Strange error in domU after dom0 update

[Andreas Florath <xen@flonatel.org>]

Hello!

I'm currently running some domUs on some dom0s. Everything is Debian  
Lenny which comes with Xen-3.2.1 and kernel 2.6.26.  The domUs are  
running without any problems.
Now I want to use live migration - which does not really work with  
Debian Lenny as dom0. Pulled xen-unstable c/s 20346 with  
linux-2.6-pvops (2.6.31.4) and installed it on an extra box.
But: it is not possible to start any of the known-to-run-very-well  
domUs on it. The domUs use a iSCSI based root file system.  They  
connect to the iSCSI-target, start to boot - but at some (random)  
point during boot, they loose the iSCSI connection with a timeout and  
therefore stop running.
WHY DOES THE BEHAVIOR OF A domU CHANGE WHEN THE dom0 IS EXCHANGED?  
Virtualization is IMHO exactly the abstraction layer which should hide  
such the dependency to any underlaying system.
Yes - it is reproducible: started the domUs hundreds of times on  
Xen-3.2.1 boxes without any problems; tried to start the domUs on the  
xen-unstable system tens of times always with problem described above.

I'm really stuck with this. Any help, remark, question, idea is welcome!

Kind regards - Andreas