I have the same problem since the release of Proxmox 2 RC1, with the first vesion of December I had no problem...
Here's what I posted today on the proxmox users list :
Subj: Still can't install Proxmox 2 with lsi 1068e sas driver
I made a squeeze install: 
 ( 
http://pve.proxmox.com/wiki/Install_Proxmox_VE_on_Debian_Squeeze ) because  since the upgrade to RC1 I can't boot on pve-kernel-2.6.32-10-pve and later  versions (grub is OK but boot locks on the access of pve VG). 
It seems I'm not alone as i have searched the forum and found : 
http://forum.proxmox.com/threads/9754-how-to-load-lsi-1068e-sas-driver-when-install-proxmox-2-1 
I've tried : 
pve-kernel-2.6.32-11-pve normal/single user 
pve-kernel-2.6.32-12-pve normal/single user 
pve-kernel-2.6.32-13-pve normal/single user 
If I boot with any squeeze kernel, everything is OK... 
It was OK with the first release of Proxmox 2 (december). 
The machine is an HP Z800 with an LSILOGIC MPT SAS BIOS C1068E SAS 1068E 
This is becoming a real problem because we had a plan to use proxmox2 and we  bought that machine for the project... 
Any idea ? 
Thank you 
Bruno