Thanks for all your suggestions. I've tried re-installing the game from scratch and slowly re-introduced each of my mods one at a time to try and see what is causing it, but.....
I have managed to save the game in the default directory now, but it still won't allow me to save it anywhere else! I am now in my sixth season and have never had any probs before. I'm now guessing it's a GP2 prob rather than VDMsound even though this was the only major change made for this season. (From DosBox to XP).
I reckon Nimrod is closest to the truth but as far as I can see, everything appears normal.
Oh well, at least I can save now, but a bit scared it'll happen again or corrupt halfway through the season!
Many Thanks again for all your time!!! =D>