Often, the attached error pops up and the workbench is into infinite loop of 
error that can be escaped only via the task manager.

Hi,

I see similar errors, when I want first close workbench window and there is 
still opened window from workbench by choice/action "Run in WebBrowser"...
So, try first close opened associated windows and then close workbench - it 
works for me... anyway, Alaska can fix this too...

    Zdeno