Project5 cannot use soft synths: TTS-1, Pentagon I

I recently installed Project5 (updated to version 2.5.1) on my Win7-64bit PC, which has Sonar 8.5.3 and X1 already installed. 

All of Project5's soft synths work except for TTS-1 and Pentagon I, which both work in Sonar.  When I try to insert either of these synths in Project5, I get this message:

"An error occurred while creating TTS-1 [or Pentagon I]."

-- Adding Sonar's VST Plugins directory to the VST folder list and then re-scanning does not help.

-- Running Project5 as administrator does not help.

Any suggestions on how to get the TTS-1 and Pentagon I working?