Thank you for your post.
I am able to replicate the issue on both Mac OS X 10.7.3 and Windows XP (SP3). I have forwarded the information to our Development and Testing departments for review. When more information becomes available, I will let you know.
One workaround is to remove the field from the tab order. "Go to Next Field" will then bypass the field.
Still an issue in FMP 12v2