Thank you for the reply. I'm not saying its definitely not a buffering problem but I don't think it is since it doesn't get printed EVER, even when the other thread is joined and prints its results. I tried adding a newline character to the end of the string, no difference.

Additionally, when the main thread exits it warns "A thread exited while 2 threads were running" as if the progress bar thread was still merrily churning away doing something (frustratingly, not printing a progress bar) when the main thread exited.

Anything else I should be checking?
Thanks
Dan