yeah i had worked that much out, really strange why adding the extra HD causes the mapping to go wrong and why it doesnt rescan (its like the scan gets interupted)
anyway i solved my problem - i had to reinstall, annoyingly because there is no way of doing a PXE install of proxmox i had to remotely PXE lenny 64bit and manually install PVE on top, but it went fine without a hitch with the exception that debian has decided to rename my network interfaces from eth0 and eth1 to eth2 and eth3 respectively, it seems persistant but still not sure about it.
just got fsck issues to contend with at the moment, but seems fine