Mail.crap
OS X's Mail.app keeps on forgetting which messages I've read and which I haven't in my Inbox.
So now I have 1000 unread messages again, and I have to (once again) go through them all to find the ones that were really unread before it screwed up. (again) I love the app for a lot of other reasons but this problem makes me really peeved.
Written on July 15, 2001