It looks like the Sprint EVO running Froyo has a major calendar bug. The bug affects users who put text in the description field of an event. Everything looks fine until you go into edit the event. Any change made to the event will delete the text in the "description" field and replace it with text from the "where" field. Is that lame or what?
Check out the video for a demonstration of the bug. Nasty! Let's hope a fix is released soon.