VSTi Problem

Hello all. I recently installed Sonar Platinum on my new laptop. All is working well apart from as issue with VSTi's. For example, I created a new track with Addictive Drums. I recorded on the track and saved. Playback was fine. I closed down Sonar. When I re-opened the file in Sonar, the midi information was still in the track but the VSTI instrument was gone. The track icon had changed from the VST icon to the midi icon. I tried the same thing with other VSTi's with the same result. Any clues?   

You'd think that, after working with Cakewalk since version 2, I would have remembered to check that first. I feel like a bit of a dill! Thank you, Scook.