Problem using eachin in callbacks?

I'm writing a callback to play some streaming sound in
FMOD, and as soon as i use an eachin loop in the callback (even if its empty) I get an unhandled memory exception. Any ideas why? My suspicion is it may be some type of GC issue.

blitzs code is not thread safe so anything that uses the gc etc in a remote thread ends up throwing a spanner in the works.

Damn- OK thanks Ant.