Thanks for the responses guys.
It is all Synths Ken. The projects are not very old. When I say earlier version of Sonar Platinum I meant towards the end of last year. Sorry - It was late last night and I was a little vague!
Any that had a patch in them had the default patch Brunddlefly.
I wonder if it was an unusual set of conditions like saving the projects with the synths disconnected and the tracks hidden and archived? This would also mean people won't notice until they try to un-archive and edit the projects. I rarely do this myself - I just wanted to change the key of an arrangement.
I always install the updates as soon as they become available. As timing would have it, on one of the occasions that a second update was issued shortly after release I made some quick changes to this batch of files and resaved them the day the first release came out. I probably should rethink that strategy:)
Anyway, good to know it has not affected everyone. It is all history now - onward and upward!