A couple questions:
1. Are you playing a version of SPWAW that you downloaded...or did you get it off a disk (mega-campaigns)?
2. When you did the 7.1 upgrade did you make sure that the upgrade took properly?
There were glitches with some of the first patches where there was an errant "space" in between the words "MatrixGames" when the file was being exploded...resulting in the files being placed in a new folder and not the correct game folder.
If this happened and you loaded the OOB 7.1 files...it may be causing the error. Now, I'm not saying that is certain...I'm not a big time tech

...but I know I had all sorts of issues when I didn't catch the file upgrade the first time around...and started using scenarios from people who had installed it correctly.
Getting the Mega-Campaign Lost Victories was the best solution in my case...I had an updated copy of the complete game at my disposal, not to mention a great campaign to play!
