Unwanted wrapping with `Auto-wrap to window size`

I have MushClient set to wrap at 137 chars width, and set the same width in the MOO's I connect to.
However, when I turn on `Auto-wrap to window size` and text arrives in an inactive window, it gets wrapped to 65, 77, or other amount of chars. If I turn off that option, text gets wrapped at the normal 137 chars I set.
Using W2K, and MushClient 3.12
[EDIT]
The screen width it wraps at is the width of the MDI screen when it's been `restore`'d, the width of an inactive MDI screen:) Hope this helps:)
[/EDIT]

Whenever you resize the window with that option set, it tries to work out how many characters to use. It appears that minimising and restoring would count as size changes.

I would leave it unchecked for more reliable operation.

I have added this to my bug/suggestion database as #400.