Sorry for the confusions...

> Not sure what you mean here
http://wiki.xensource.com/xenwiki/NetBSDdomU

Before the first reboot there's a suggestion to:
mount /dev/xbd0a /mnt
cd /mnt/dev
cp -pR /dev/rxbd* .
cp -pR /dev/xbd* .
halt -p

It was about an older NetBSD 2 domU install but anyway I have actually
tried without this however same hanging occur.

> I don't understant what you mean here. Is the Xen box you desktop too ?
> Otherwise how could a ssh session make your desktop swap ?
> When you says the CPU is 100%, is it dom0's CPU or domU's CPU ?

No. I log into the dom0 via ssh (server room is a bit away+cold+noisy...)
From the ssh console running on the dom0 I start up the VM as root with -c
paramter of course then I log into the VM as root. 5 minutes later it
stops responding. In the meantime I have another dom0 ssh connection and
that shows the CPU load to be 100% and the fully used 512M memory by xm
top.

When this hanging happens it drives my desktop Fedora nuts. It becomes non
responsive too and start swapping... I didn't understand this neither but
let's not worry about my dekstop. :)

> Xen's scheduler parameters. Changing this to have a non-0 minimum time
> slice
 Could you point me to the right place about it? I don't understand this.

I really appreciate your efforts.

Thanks
Ivan