I use Sonar X3 Producer. In the past I had no problems when exporting mixes to stereo wav files. However, now, when I export a stereo mix to a stereo wav file it comes out in mono. Any ideas?

Please be precise.
Is that what you hear STEREO?
Is the exportet file a Mono-file - or a stereo-file with both channels the same content?
I can remember that it was already happining that one single mono plugin - somewhere in the project - can force the whole export to Mono.

First thing that popped in my mind is mono reverb or compressor on master buss.

THambrecht
Please be precise.
Is that what you hear STEREO?
Is the exportet file a Mono-file - or a stereo-file with both channels the same content?
I can remember that it was already happining that one single mono plugin - somewhere in the project - can force the whole export to Mono.

Bingo.
 
First step is to determine if the exported file is actually mono, or if the left and right channels are identical, meaning: does it contain one channel or two? You can quickly determine this by looking at the file properties in Windows Explorer, which will give 2822 kbps for a stereo file and 1411 kbps for a mono file (assuming 44.1 KHz sample rate).
 
If the exported file is determined to be stereo, the source of the problem will be found on your master bus. Either the interleave has been accidentally set to mono, or there is a mono plugin in the fx bin.

Thank you guys. I found the problem. It was a simple thing. a speaker cord in my monitors came lose and was making contact. I pushed it back in and now there is stereo. Problem solved. Thanks for caring. All the best for you all. Jerome