well im working. not that my autoloader working has anything to do with the 4 wasted hours i spent on the phone to symantec support!
If anyone is intersted here are my notes from the call in case you want to go through the same process. In the end my fix was to remove the two LTO 2 drives I had attached to a different scsi controller (these were being retired anyway) and move my new 1/8 G2 autoloader to the "old" scsi controller. After this i was able to backup and restore with no problems at all.
drivers set to correct versions as per symantec recomendations.
sent diag logs
removed all tape devices with tapeinst.exe
reinstalled mdac 2.8
downloaded driver pack from http://seer.entsupport.symantec.com/docs/289147.htm
was driver patch for wrong version (clever support engineer!!)
installed correct version(which was already installed if the support engineer had checked my hotfix installations or asked)
rebooted
ran tapeinst.exe
shutdown server
powered down device
started device
started server
At this point it was still failing and i shutdown the server, swapped the scsi controller it was using and everything worked fine form this point.
Good luck hope this will help some people!