Hello Brian Flynn:
Thank you for posting.
I was able to replicate this change in behavior from FileMaker 11 to FileMaker 12. Although this may be a design change I have submitted this issue to Development and Testing. I will update you once more information is made available to me.
I have a similiar issue with aligning repeating fields. The way I got around it (for the moment) is to turn sliding off.
In inspector just uncheck anything that has to do with sliding.
It's not a permanent fix, IMO, since now I have tons of blank space but at least it is properly aligned.
Thank you for posting your workaround.
I added your post to the original report of this issue.