It has been observed that when you have backup exec with SEP you get LU1845 on the liveupdate screen while liveupdate is going on.
However if you will run the live update on a computer without Backup exec it wont give you this error.
Well for now you can just ignore the message because it doesn't affect Definitions update.The virus definitions are downloaded fine without any problems.
Most probably Symantec will take care of this error when they release a patch for SEP.