Well DJ, the FSX root path is not where flight plans are saved. My FSX is on the D drive but the flight plans are saved by default in C:\Users\Iain\My Documents\Flight Simulator X files.
So I need two locations to save not one. I'm using FSBuild 2.4 btw, on Win 7 64 bit. This plan saving was working fine when I had both FS9 & FSX on my machine. However, to avoid wasting disc space I have uninstalled FS9 and that was when the trouble started. Sorry, I should have explained this in my OP.
That's fine - all of the FSX plans should be in that location by default on a Win7 System. All of the plans for individule add-on aircraft should be in their normal positions. For example if you have FS in D:\FSX then the default FSX plans will still end up in your My Documents folder as before and when you set the FS_HOME path to D:\FSX then (for example) you will see the PMDG path as D:\FSX\PMDG\Flightplans. What are you seeing?