My apologies, this issue seems to have resolved itself.
I compacted the database with File Maintenance overnight, re-booted and can now access and configure the plugin without the problem happening.
Obviously something screwed up in my setup.

No problem here.

Generate debug log http://www.mediamonkey.com/forum/viewtopic.php?f=6&t=69 and attach it to support ticket so that we can look at it.

As above, editing the configuration of out_wasapi.dll causes mediamonkey to lock up and generates an error pop-up.
I have completed the request for information and sent to support.
I had to use Task Manager to exit MM

I am able to reproduce this every time I try to edit the configuration for out_wasapi.dll