Cubase 7 64bit VST Instrument GUI slugginess

For some reason I am experiencing a problem with Cubase 7 64bit (latest version) that some of my vst instruments are behaving in a way that the GUI is very slow and sluggy. I am experincing this with Spectrasonics Omnisphere for example, it takes me around 7 seconds to see a patch list whereas in 32bit cubase it takes only 2 seconds.

Strangely I am not experiencing any of these problems in 32bit version of Cubase, or in any other DAW I’ve tried - only 64bit version of Cubase seems to be causing slugginess and hanging.

Any idea how to start troubleshooting this??

Are the plugins you are using bridged?

No, they are 64bit such as Omnisphere.

Did you try to start Cubase in safe mode and/or remove preferences?

I haven’t tried that yet, could you instruct me how to start cubase in safe mode, or how to trash preferences? Thanks for the help![product]=296