Game window too small?

Hey Unity people,

A couple of users encountered a strange bug on Windows.

What happened was that the windowed version of the game would only display at a fixed (rather small) size. Full screen worked as expected, but no matter what resolution they chose in the "Resolution Display Dialog" they always got a very small window (their estimates were ~300 pixels across).

To fix this problem, the users deleted their preferences (from the Windows registry) and all was well again.

Any ideas on this? Has anybody else seen behavior like this before? I've not been able to reproduce this problem. [My test machine is Windows 8. I think one or both of the beta testers were using Windows 10.]

Thanks.