"Processing audio data" during mp3 export

[Sven]

I've got a  project with about 50 tracks but it now seems to have a new lag time 'processing audio data " before it starts the export mix ("mixing down audio").  In the past with large projects it would start chugging along export/mixing right away and I could monitor the progress immediately.   Is there some setting I might have changed that is causing Bandlab to need to process audio data first before export/mixing?

The tracks are a combination of audio tracks. soft synths, and archived tracks of both types.   Everything is the project is the same as  in my previous projects.

Thanks.

[mark skinner]

Sven , my win7 i5 quad ssd ,  has always had extra processing time exporting anything as mp3. wav goes straight to exporting , unless I've done some time stretching on any tracks without bouncing it afterwards.