Thanks for that - I've tried the compability options, results as follows:
NT4 mode - Paradox runs OK, editor problem remains.
Win98 mode - Paradox will not start - "Could not initialize BDE: insufficent shared memory available"
Win95 mode - as for Win98
Win2000 mode - Paradox runs BUT dialog boxes have anaonymous buttons that don't work!
(As an aside if I load the forms into 'Paradox for Windows' [V 4.5] I can change the form sizes OK, so it's not a problem with the forms themselves.)