audio mixdown mp3 problem

Hi,

When I do the audio mix down to export my project to mp3, the mp3 file is created and sounds like the original if I import the file back into my project. If I listen to the mp3 (same problem with wav), the song is there but plays in slow motion (both tempo and pitch below where they should be). I have tried the playback on my laptop and on my phone. I have checked that the project setup sample and bit rate match the export sample and bit rate. It happens with standard export and real-time. All tracks in the pool have same sample and bit rate. If I load tracks from the pool into a new project I get the same problem.

Any ideas on what I am missing here?

Thanks,
mark

Windows 8.1 dual core with 8GB RAM and 64-bit OS
Cubase LE 6 (Version 6.0.5 build 357 (64 bit))