Hiya's,
Some great news and a bit of bad news
Well i have played and hit a merchant somewhere near Hull, then i skipped out to sea eastwards from hull in pursuit of a lone merchant
Weather was rainy and windy vis was bad, dived/listened/surfaced to get a line on the merchant, just as i was sure i had spotted him pow, sh5 crashed me to desktop and the game was instantly shutdown
So i am getting closer to a stable game at last
Ohh and the mouse movement was slick

not a single stutter and i could pan round as fast i wanted and everything was instantaneaous
Think i disabled v-sync in game options but will check asap
Game Settings ..........
High, AA on 2x (1 notch to the right, think 1 notch but will check)
In ATI CC settings are ..........
AA use app settings
AF use app settings
AI Disabled
MipMap High Quality
Wait for Refresh - Off unless app specifies
AAA Unchecked
Triple Buffering Unchecked
And i didn't try xfire with the above settings, but i bet xfire won't work or at best i'll get stuttering
Gonna have another quick sortie, if i get time i'll add the deffo game option settings