Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_1 like Mac OS X; ja-jp) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148 Safari/6533.18.5)
Well looks like I'm not alone. I can bet there are many other people with the same problem because why else would it be happening.
The other question to ask is the Apple ID you're using a MobileMe account or other? It could be that if you're using a MM account you may not have the problem. Mine is a gmail Apple ID.
I recall a gmail iOS Mail issue a while back. Maybe this is the same problem? For those of you that don't have a problem, are you using MM?