1. Auto Number:
http://boards.developerforce.com/t5/Apex-Code-Development/UNABLE-TO-LOCK-ROW-error-during-deployment-SFDC-bug/td-p/208792
2. Update same record @future
http://boards.developerforce.com/t5/Apex-Code-Development/Unexpected-quot-UNABLE-TO-LOCK-ROW-quot-on-simple-update/m-p/175859#M27475
http://boards.developerforce.com/t5/Apex-Code-Development/UNABLE-TO-LOCK-ROW-unable-to-obtain-exclusive-access-to-this/m-p/155429#M22439
3. official doc
http://www.salesforce.com/us/developer/docs/api/Content/sforce_api_calls_concepts_core_data_objects.htm