Ugh, I've been having so many problems lately.
basically I'm exporting a video in prem pro. The media is all on an external drive connected via USB.
throughout the export the "auto play" message kept popping up as if it had disconnected and connected by itself, as well as many messages about how the drive needs to be formatted (it doesn't).
in the end, "error compiling movie / unknown error" caused the export the stop and fail.
error compiling movie / unknown error
if you 'Google' the message it throws up several reported occurances and suggested solutions which may be of help.
The fix was.... changing the USB port on my computer. The front two for whatever reason kept disconnecting. I tried one of the rear ones and it's been working fine which is a HUGE relief as I really was about to pull my hair out.