Yes I've had this issue but not on all the photos uploaded to picasa from the phone. Seems fairly random. First I thought it was size related but I've seen it on photos of varying sizes.
From what I've read, it has something to do with the Sense uploader for picasa. I think there's another app on the market that lets you upload without this issue but the app isn't as well integrated with the gallery. If you do a search, there's a thread with a link which explains it better.