Changing patch crashes MainStage

Hi All

I'v recently updated my laptop to Yosemite and the latest MainStage. I've been using the programme for several years.

I now have a bug which crashes the programme if I try and re-order a patch. The thing locks up and the skinny wheel appears and doesn't respond.

Has anyone got any suggestions as to why this might be happening?

Thanks anyone and everyone in advance :-)