A single straight update statement all by itself can't cause a deadlock with another update/insert/delete statement. So, other statements within these query batches must be involved. Since you're on 2008, you can use the system_health extended event session to look at the deadlock graphs. That will tell you the other statement where the deadlock is occurring. What's likely is that you're doing two statements that involve both reading from the table and writing to it, but they are doing those reads and writes in different order. Understand all the statements involved and you'll be more likely to arrive at the solution to the deadlock.