Don't You Hate It When....

When doing a barbell bench press (could be other exercises I guess), one pec seems like it cramps up more then the other? This happens very rarely, but it happened to me when doing triples tonight. Seems like I want to stetch out the other pec or do something to get the same feeling.

Anyone else have this happen to them? Anyone know what causes this? Is this just a very minor cramp?