Have tried these solutions with some success. When I try to activate Vista it happens that activation fails.
DNS problem solved by re-entering the product key (or use "slmgr.vbs ipk <product key>" ffollowed by "slmgr -ato" from the commandline)
Product key unaccessable solved with see http://support.microsoft.com/kb/917050/en-us (describe Windows XP but worth trying)
Other interresting solutions see http://support.microsoft.com/kb/931276