I suggest you check the userforms' specified heights & widths; the one you uploaded is set to 631.5 points (~8.77in) high & 2334 points (~32.42in) wide. Unless there's some obscure form of file corruption at work, the most likely explanation is that someone has edited the userform dimensions.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Yes, that I knew. Sorry, I guess I wasn't clear at first. All the forms have had their properties altered, but nobody has access to my PC and that's the only place they're ever edited. Also, nobody in my organization understands even the most basic concepts about VBA. If this is malware, it seems like a seriously pointless payload.

And beyond the fact of the forms being resized is the question of how their controls, which were also resized, can be restored to their original dimensions & proportions just by changing the form's width in the Properties window (by any amount). That doesn't jive with my long experience creating and modifying userforms.

I've kind of surrendered right now & written macros to correct all forms' dimensions if this happens again. But I was hoping for some clue to why it happened at all.