Alpha 2 already has Xen 4.1 packaged and ready for testing. It appears to be known bug that HVM  DomUs crash at Xen 4.1 Dom0 with different "pvops'' kernels ( in particular 3.0.0-5-generic Ubuntu) , but not only on Ubuntu . Here is report for Fedora 15 : http://www.gossamer-threads.com/lists/xen/users/213049?nohighlight=1#213049 Ubuntu developers are pretty sure that Xen Host will be built with no problems. Would it  be possible to issue a patch for Xen  4.1 to fix the  problem ? Actually two distros are affected Fedora 16 and Ubuntu 11.10 ( maybe Debian  - here i am not sure ) Boris.