I noticed that this has started happening on my system.   On random occasions, after pressing the + sign to insert a synth, the "Insert Synth" will be greyed out.   Happened just now on my system.   Tried:
 
1.  Closing project and re-opening - Still greyed out.
2.  Close Sonar and reopen same project - "Insert Synth" now available.
 
 

Well, I 'm sorry to hear that Davec, but perhaps if anyone experiencing this bangs in a Problem Report, the Bakers may read one of them and take some action. [hope triumphing over experience again]

In my updated version of Sonar Platinum the synth rack can't be accessed like it used to with the big + and - buttons. I would like to add some Native Instrument synth software but can't find it in my DAW or install it into the program. Could some one kindly tell me what my efforts of several hours cannot solve?  Or has this question already been answered.  Basically I'd like to add a new plugin!
Thanks