I've experienced the same thing... I've noticed that it only happens when the first item on the list or library is targeted.
I had a list where item # 1 had no targeting and a few others did. It all looked fine until I targeted the first item and then all the items got messed up. I removed the targeting on the first item and all went back to normal.
I then experimented some more: I targeted an item further down the list, leaving the first one untargeted and everything was ok, but then I sorted the list by modified (instead of name) and hey presto... GUIDs again!!
So basically, targeting the first item on the list is what messes things up!