I inserted an SI Drum Kit Soft Synth and played around with it. My immediate impression was that it would be great to make it tempo driven, so it started and stopped with the song rather than using the infinity loop. And Lo and Behold, there in the options was a tempo-based ...option. BUT, when I selected it and closed the DBox, I got an error that said an unsupported action had been attempted. I got the same error whatever I asked for, including unticking all options. So I figured that maybe I had inserted the synth as the wrong type (Simple synth, First Audio etc)and so historied back past the insertion. The SI drum synth has gone. ...Any help appreciated. EDIT: Just tried it with SI Bass and even though I made absolutely no changes, the same thing happened. Closing and opening SONAR does not help. The synths are gone. They still appear in the Plugon Manager as enabled but they are not there in the list of soft synths.

"And Lo and Behold, there in the options was a tempo-based [Effect] ...option." 

That one word,'effect", is pretty important.
I've been trying to replicate your scenario, but only have partial success.
What I have seen is that checking Configure as tempo based effect moves SI Drums from the VST Instruments category to the Vst Audio Effects category.
However, I can still insert it as a synth. I have not rescanned, which may be a factor.
For whatever reason, I have not triggered the problem, but I can see where it is ready to occur.
Note that Configure as synth/Configure as tempo based effect are radio buttons. Clicking one toggles the other off.
SI Drums is, in fact, a synth, and should be configured as such.
I don't know why the SI Bass would be affected, but double check it as well.

A tempo based effect would be something like a delay that gets its timing from the project tempo, or a flanger that syncs to tempo.

Once Sonar reads the SI plug-ins as synths, that should take care of the error problem.

Now, back to what you were trying to do in the first place.
The SI interface is self contained, but is synced with your project BPM. You can play with the various patterns, but they will not be integrated into your project.
For that to happen, you need to drag a pattern from the SI GUI to your MIDI source track.
These are groove clips (loops), so if you want to repeat them, just grab the right edge and drag them out.
Think of the SI GUi as an auditioning space befor you commit the patterns to your project.
Hope that helps.

Thanks for the reply Shimozu-Kushiari. I can see it as an audition place, fine. But what I wanted was to have it start and stop automatically as I stopped and started play, while I was sorting out drum patterns, sets etc. However...the trouble is that I can generate the error just by opening ghe VST dropdown, choosing Plug-on Properties, then hitting OK. The piano and Strings remain visible / usable, but the drums and bass have just disappeared. Because, as you say, they have become FX. So the way it stands, I can generate the error even if I do nothing, but even with the error, I still get a result. So I guess my question is, how do I get drums and bass back as Synths? And why is that error flag showing?