I am having an issue when trying to test scripts with mushclient through wine. Every time a script has an error, and attempts to display the error in a window (which looks like it would be a notepad window), mushclient crashes.
There have been intermittent reports about crashes when using the Notepad under Wine, which I haven't been able to reproduce. In the past, upgrading from Wine 0.9 to 1.0 seemed to help, but you seem to be above that version.
I'm not sure what to suggest, you could certainly try opening a notepad window manually (eg. Ctrl+Alt+Space) and seeing if it crashes straight away. If not, try to find what makes it crash (eg. typing into the window).
If I could work out what is responsible, I can probably work around it, but as it doesn't do it for me, that is hard (needless to say it also never crashes under Windows).
Maybe it is something to do with the font you choose (or have installed), some Wine configuration option, screen resolution, or something like that.
I had this issue before and solved it by using Wine's own notepad instead of MUSHclient's built-in notepad.
The crash seemed to be caused whenever MUSHclient's notepad tried to open. Any attempt at opening the built-in notepad resulted in the client crashing.