I just had that happen tonight when I installed Dorchester and Rapture Pro and then scanned VSTs. I'd like to know what's up, too. I finally clicked the little "x" at the upper right of the pop-up that was demanding to know the path of my Waves plug-ins because it wouldn't accept the truth as an answer. I had to click it many times as it wouldn't give up asking. Now, of course, Sonar doesn't see my (many) Waves plug-ins :(
Thanks for bringing this up, because I thought I was alone and was hesitant to mention it since I thought it was probably some bone-headed move I made that caused the problem to begin with.