Hy kelly,
first excuse my poor english,
i have quiete similar system specs (Ati instead of nvidia VGA) but also nforce and AMD cpu. SH3 runs very well and without crashes, but telling you this won´t really help you
.
The micromanagement buttons are those icons on the lower right side of the damage control screen (the one with your uboat and those little men) were you have profiles for surface cruising, under waterattack etc. For example pressing underwater attack will send crew to the e-machines and torpedorooms and so on instead of moving every single man to his battlestation. Some users have reportet crashes when using them.
If the crashes occour without using the buttons you have to go the hard way of fixing the problem by trial and error.
First make sure you have no further programms running in the background when you start game (Antivirus-soft, filesharing, etc)
Someone told the about a programm called "end-it-all" or something, used to end background processes. Sorry, I have no link.
Are your drivers up to date? If not think about updating
Are you using beta drivers? Not good...use official drivers
Is your system overclocked? Not good...
Some users reported they have fixed crashes by toggeling hardware acceleration for their soundcard down. Use dxdiag (included in your OS) to turn it down.
It´s quit hot these days, maybe temperature problem with you machine? Use a programm like "everest" to check sensors.
Check your memory with a testing software, i recomment memtest86, included in several linux distris.
Good luck on locating the error hope don´t have to spend a lot of time bugfixing, playing SH3 is more fun...