I'm running a top end machine w/ win7 so I figured I could change frame limiter to off, remembering that I first played through this game on an athlon socketA running win2k.
This was a huge mistake; not only did it cause the boat to go so slow that the boat mission was impossible even with a perfect run, but it also caused my cars to have problems going into reverse. Certain cars wouldn't back up at all, and those that could took a ridiculous amount of time to start backing up. And those cars that could back up were impossible to back up on beach terrain.
Hope this helps.
PS: I wouldn't have figured out my issue so quickly except I happened to see this thread. Thanks!