Sounds like a db lock to me. Are you sure there are no new processes that have been introduced into your workflow recently that could be causing contention?

You should log the database activity using Enterprise Manager and pore (paw?) through the results looking for inserts and/or updates that could be occurring at the same time.

If you can't find out yourself what changed (because remember, your program didn't change, its environment did), then ask around in your workplace. It just might be that you run into someone who says that they moved a job back from 8am to 7am because they need to run some reports afterwards that have to be ready at 7:30.

Good luck.