Logic Pro 9 Sudden slow playback on certain tracks



This is something Logic Pro 9 occasionally does and it seriously pi*&es me off and I don't know what causes it, but now I have a track to mix for an EP and its happened again bringing the project to a standstill - gggrrrrrrrr!!!!

In a nutshell recorded a bass chorus part, then copied it in the track to the next chorus. Played back the track first chorus fine, second chorus (the SAME wave) plays back at 20 BPM slower than the previous.

Tried re-recording it with exactly the same result, emptied unused audio from the audio bin closed Logic, re-opened still plays the track at different speeds.

This disease has now spread to the verse section and the bass track on that (again copied audio from its own track) suddenly slows down the 3rd time its played.

There are no intensive plug ins in use, no CPU or hard drive meter activity I am completely stumped why the feck causes this???

Can it be fixed???