If you use IDENTITY columns in your tables, you can expect problems with your identities getting out of sync. The problem will show up in client error messages and in the SQL Server ERRORLOG. The problem is particularly evident after unplanned reboots and failure of badly written queries that attempt to insert or delete rows in the identity bound table.
The fix is easy: run DBCC CHECKIDENT.
I keep a couple of scheduled tasks ready to fix identities. The tasks are both based on the same stored procedure: check_ident. One task calls the procedure Without parms. This will check and fix every identity in every user database on a SQL Server. The other is setup to supply a database name. This is easier to walk someone through to fix identities in a single database during off hours or when development causes an identity problem.
The stored procedure is also useable as an autostart job that is run whenever the SQL Server is recycled. See the Books on Line information about sp_makestartup.