Hi Mark,
Thanks for your response and usual good advice.  There were 3 other downloads that the fsdeveloper thread insisted had to be done or FSX SDK wouldn't work.  Are you familiar with them and are they really necessary?
My original FSX installation was Delux. I recently bought FSX Gold in order to have Acceleration and tried to install SDK from that disk (there was no information to the contrary), so I think that's where my problems started.  During the installation it said SP1 had to be installed, which I did, but nothing about SP1a, etc.  I'm going to have to uninstall eveything connected with SDK and try a reinstall, but I need to know about those other (seemingly unrelated) applications that fsdeveloper wrote about. Are they really necessary?