[CentOS] can not install CentOS as VM in KVM

Hi to all,

I am trying to install CentOS 5.5 as VM on a KVM server running Ubuntu
10.04. The Problem: the installer does not find the iso image. (Direct
copy from website downlod.) I can start CentOS from the iso and can even
do some disk checks. But when I go further the installer says "no CDROm
found". Pretty weird. I tried all CentOS 5.5. image available (Live CD,
net install, bin 1 of 8, 32 bit and 64 bit).
Other installation (Debin, Ubuntu, SLES, Windows XP, Windows 7, Windows
Server 2008) worked fine.

Perhaps somebody can help me in setting things up for that.

Michael