hi Damo
i have read your post and i am hearing mod conflict alarm bells. i know you have spent along time splicing them together, but something like this happend to me
"not so long ago..." if you pardon the pun!!
it was Racerboys SH4 Special Effects and Thomsens Sound Pack. it started first with loading and finding the crew without wet gear in the conning tower when i had saved surfaced in bad weather with the crew all dolled up in Oilskins..
then your problem started and it would not load even when i went back to previous good save. in the end i scraped the patrol and pulled out one of the mods. since then no problems: i hope someone else has a better solution, good luck
by the way, your rig is plenty. i have amd athlon 3800+, 2gigs ram and 7800 nvid card and it runs very smooth