Upgrade vCenter 5U1 to 5.1 fails

Hi,

trying to upgrade my vcenter server to 5.1 but getting the below message

error 29114 cannot connect to db

I have tried this with a local express DB and a full 2008 R2 DB server and get same results. After trying that ive tried building a new vCenter and i still seem to get the same error. Can anybody point me in the right direction to fix this?

Thanks