Found, initialization bug. No wonder no replies to this. I had to add to the same layout the same global field and add the same drop list from the other file that wasn't dropping. Then the new field and old field both started working. I removed the new field and the old field continued to work. I so far have had to go to every layout with the other files remote value lists and repeat the process. Really, no one has seen this before?
Sorry for the late reply. You've probably already solved this one, but just in case it helps, here's my diagnosis: dynamic value lists are compiled from the field indexes, so it sounds like the index of the field that is the source for the list was nuked during the conversion. I suspect the field causing the problems may have Field Options > Storage > Indexing set to "Minimal" with "Create indexes as needed" checked. If you're still having the problem, you can try changing the Field Options > Storage > Indexing setting to "All," which will force FileMaker to build an index for the field immediately (could take more than a few seconds for a large database). Likewise, if you're ever experiencing problems with an indexed field, you can rebuild the index by first setting the Storage option to "None", save the changes, and then go back in and re-enable indexing on the problematic field.