This is not really a bug.......it's really metro telling you something is wrong................
I had Metro saved on startup as mono CD quality (44.1 and 16bit) as I was mucking around with some old time radio tracks.
When importing a stereo track 6.0.7.1 puts the stereo track into the designated mono track 1 and when you hit play a -36 I/O error appears. (I could be wrong about this only happening in 6.0.7.1 as I don't have the older versions to check it on.......it hasn't happened before though).
Anyone coming across this should make sure the digital audio settings in the setup menu are equal to any audio you're about to import.... well that was my solution.
Can different rates be played together??
Other errors on hitting play are in the metro faq and are as follows...
A series of errors upon pressing play, such as:
-50 Error in parameter list/not an existing volume/bad positioning/bad drive number
-225 Invalid sample rate
-229 invalid input device reference number.