rabeach
I believe you have to run sonar as administrator for pentagon to work.

I don't believe intuitiveleap has pentagon since s/he only has Platinum.
 

Pentagon has cool sounds so you want it to work.  I don't run it as Admin, and it works fine (CAVEAT: if you flip through the presets fast enough, you can get it to crash Sonar and your audio driver and almost blow your monitors up before you can hit the kill button -- bass monitor speakers looked like they were trying to bulge out and smack me in the face.  If you try harder to get it to crash, Pentagon can jam up the output meters with a sustained inaudible high frequency you won't notice until smoke pours out of your tweeters ... there goes a couple hundred bucks!  But other than that, it sounds great.)
 
The dll should reside inside "C:\Program Files\Cakewalk\Shared DXi\Pentagon I" folder, and the dll size should be 2,935 kbytes using Windows Explorer.  There should also be a P1DXi.dll in that folder with size of 312 kb.  There should also be a subfolder in there entitled "rgcaudio Pentagon I".
 
Do a search of your whole harddrive for "Pentagon" and see if you have some duplicate pieces floating about.  If yes, move them to a temp folder inside of MyDocuments where Sonar can't find them.  Rescan. 

There's also a Registry hack which might be required to get Pentagon to work.
 
I'm not at my DAW so can't confirm, but you need to locate where the program dll key is located, right  click it and modify the Properties.

Ok, your registry may be fine but check what's here:
 
HKEY_LOCAL_MACHINE\SOFTWARE\rgc:audio Software\Dxi\Pentagon I
 
It should have a string value called Path set to something like this:
C:\Program Files\Cakewalk\Shared DXi\Pentagon I\Pentagon I.dll
 
IN ADDITION, you may need to run SONAR as admin for it to load.  
 
Keith

For Pentagon, pretty sure it is possible to avoid running SONAR as administrator, see http://forum.cakewalk.com/FindPost/3319219 for instructions.

Yeah, that's a nifty approach (setting the subkey to allow anyone to access it).

Even though the plug-in is no longer bundled with SONAR, it still might be useful if one of the devs knocked out a quickfix program to update the registry and add it to the knowledge base.

 
It's probably worth repeating that intuitiveleap doesn't have Pentagon.
 

Yes, the user should not have hijacked this thread. If they want to have their problems addressed a new thread would have been a better idea. That said, it is not too late for Cakewalk to publish a quickfix for Pentagon.

I had tons of probz with Pentagon a while back. I even bought it separately at one point but somehow SONAR got confused and wouldn't load older projects that had it. New ones would load fine but un/re-installing it didn't fix anything. Luckily I had a demo bounced down with the sound pentagon made isolated so I turned it into a sample instead.