Cubase &.5 constantly freezing & unresponsive

Been having problems with constant freeze ups and having to force quit.

I have Cubase 7.5 Imac OSX 10.8.5 8Gb Ram 1 TB hard drive 3 TB Ex hard Drive 5 CMC midi Controllers My keyboard Midi controllers are Arturia Keylabb 49 and a M-Audio Air 61.

I use the iMac just for recording purposes.

This problem has been there since I purchased C 7.5 by download 5 months ago I also had issue with My M-Audio freezing but this seems to have resolved for the time being but I am using the Arturia now for the most part which never freezes. I also had problems with a Liquid Rhythm VST which was a bug now resolved. Initially I thought hardware and third party VST’s were to blame but it happens regardless.

Cubase will freeze shortly after loading a project template without loading any VST instruments just messing around with the percussion track and halion loops or after loading an ongoing project. It’s unpredictable.

The Chorder midi instrument which came with Cubase will not display presets so is inactive.