Plugins - can't view ?

Hi there.
 
I would appreciate your help here in rainy UK.
 
I'm fairly proficient re Sonar 8.3 and it's running fine 64 bit win 7 on i7.
 
But i have a strange view problem thats driving me nuts. In some projects when I double click on a plugin (mostly sonitus) it opens up but i can not see it on the screen. The plug in works and can be turned on and off but I just can't manage to view it. On other channels  I can open same plugins fine. I have a feeling is a screen viewing problem. I have played with the floating settings and tried bitflippers Alt spacebar to no avail. I'm sure its something simple[.
 
Any ideas.
 
Much appreciated