Thanx Matt for your input, I suspect I had some type of virus so I ran a scan....nothing showed up. I am running Windows 7 64 bit and am running BIAB 2011.5 on an internal drive on my HP laptop. I have used the ACW many times before without this problem. I also get a similar error code from RB when trying to run ACW there. I've been trying to check file associations to see if that might be the problem but no joy. I have given full control for permissions to see if that might be the culprit....no joy. I will look for the UAC but isn't that the same thing as Permissions? Oh, I forgot to mention that I can open Midi files and native files on BIAB but cannot import mp3 or .wav to ACW!!