If this is not related to SH3 Weather then see below.....
You did not state whether this was a new installation of GWX, so....
Career saves that were created before the addition of GWX are NOT compatable.
GWX has made so many widespread changes to the stock game that I'm affraid you will have to start a new career.
Welcome to GWX.
EDIT - It's not clear from your post. So, stating the obvious, did you just add the 1.03 patch or did you download & install the GWX base files first. There are 6 parts in total, 1 x exe & 5 x bin files, then add the patch.