At least two people couldn't reproduce the issue (and new games in XBC work just fine for me, so that makes three...) so it's probably a problem specific to something you're doing. Verify the integrity of your disc image. Right-click the games in Dolphin, go to Properties, head all the way right to Filesystem, right-click on the first thing you see there and check for an option that checks the disk's partitions (or something to that effect, I forget).
Any errors mean you have a bad dump, in which case you should dump your games again.
Any errors mean you have a bad dump, in which case you should dump your games again.