I've attempted to reproduce this bug, and can't. Can you confirm whether this is still causing you a problem? There was a major rewrite in this region of the code recently (but I can't remember whether it was pre- or post-beta11).

If not, can you confirm whether there's anything particular about the numbers that are causing you problems? For example, do they have 8's and 9's in them? How many digits (the limit is 8 by the way)?