>>were doubled, and some weren't. So, I called in, grabbed their data, and verified the problem. So far so good.
>
>This was your lucky day. I don't know how many times I have told people I can't fix and error that I can't duplicate.
>
>Of course, running two systems with the same code and different data should have pointed you to the data right away. Not that it WAS a data issue, but sometimes our test data doesn't throughly test our code properly, cause we don't do the stupid things that users do, such as add empty records.

You're generally correct. However, in this case it didn't work. My client had added two empty records (she only meant to add one) so that a drop down combo would allow for blanks. So the ultimate, ultimate bug was that I hadn't given them this option. I never would have thought to do that, and she hadn't connected to two facts. No reason she should have, of course.

So, two more principles this illustrates. 1) Don't get distracted by the usual cause of a common symptom. 2) By digging down into the real cause of a behavior, you might find more than one bug. We have two...I don't allow blanks in a lookup field (doh!) and we allow blank rows in another form.