Debugger Error:Invalid scope kind

Hi this has been asked before:

http://www.blitzmax.com/Community/posts.php?topic=54306&hl=invalid%20scope

...but didnt receive any responses so I thought I'd see if I have better luck.

I've just stepped through my code and received this error which I've never encountered before:

'Debugger Error:Invalid scope kind'
Process complete

..and the application obviously ends. I've no idea what it means - any ideas?
Thanks!