more often than not the reboot is down to lack of network connectivity between your client and the server,usually because you lack
Vista Network drivers in your
boot.wim file which is used to load WinPE which in turn installs the OS for you,
as Torsten says, look at your SMSTS.log file to find out if it is indeed a network problem,
do find out how to do that, see
this post if you don't understand what the errors in smsts.log file mean, post them here and we will help decipher them
cheers
niall
my SCCM step by step Guides >
http://www.windows-noob.com/forums/index.php?showtopic=1064