Actually, I've run into several problems re-loading saved games multiplayer - possibly related.
I tend to save my game 2-3 times to different files just to make sure I have a good one. You'll know whether it will work right away because when someone joins and it starts the file compression, normally this will take about 15 seconds, while when the bug occurs it usually takes no time (obviously fails somewhere).
I've "fixed" this problem by having everyone exit the game and re-enter. Failing that, loading the game in single player mode, saving it to a new file, and loading that file multiplayer works (I do this by habit if we're restoring from an autosave).
My guess is the file you're refering to has compression-data in it, and by deleting it you cause the program to re-do the compression - Which (just guessing) seems to be the problem with the never-ending load cycle.
Anyway, just my $0.02.
By the way, I rarely see anyone from Paradox scanning this forum - Do these bug reports ever get to them or should we re-post these sort of bugs on the bug-forum?
Waffen