It turned out to be FOXUSER.DBF that was causing the problem.
I was surpised when I first read up the help on reports and looked through a couple of books, because they get barely a mention. Then when I got to the writer itself it looks postivelly bare...and that's compared to VB's lame effort, let alone Crystal or Access. I assume (coz I've only just started using it) that it does more than is immediately obvious otherwise it would be next to useless. I've tried looking for more info about this report writer, but everything seems to point to using Crystal for your LAN and Acrobat if your internet programming. Sorry, but coming from the outside world the report writer looks like an afterthought.
Anyway, what I really want to know is whether I can get programatic control over a reports structures like I can in Access.