I'd also check the memory usage for the SQL instance. Compare it to what was being used before SP3 was applied. I have seen SQL Server start escalating to table locks when the amount of available memory is insufficient for the current activity.

In particular, this occurred to us one time when someone fired up a memory-hog application on the server, robbing SQL Server of it's normally available amount of memory.

I have subsequently changed from allowing SQL Server to (entirely) dynamically allocate it's memory. I know specify an appropriate min server memory and max server memory. The min server memory is appropriate for the amount of activity anticipated for that server.