Then I choose an active preset: Unison and another (seams to happen with different presets).
Then I went to edit - inserted a band before the current band with the unison effect.
Then I inserted a band after the band with the unison effect and cubase crashed.
I inserted a band after unison again without adding a band before the first one....another crash.
It happens only with inserting a band after.
Great thanks Vojtech.