Firstly, welcome to the forums!
Onto your first problem. This is almost certainly a graphics issue. Silent Storm is unfortunately ahead of the technology on most PC's when it comes to graphics. If you go into the graohics options from the main menu, make sure you've got 16bit colour selected and not 32bit. That should be next to the resolution you're running the game at.
Also, you might want to turn off the tree tops using the checkbox near the bottom of the graphics settings.Missions with a few spots of wooded area will cause the game to run slowly.
Finally, try switching the cursors from Software to Hardware. If you like the original cursors and want to keep the same look but with less lag, there should be a download here that will help: http://www.strategyc...dex.php?dlid=51
Onto your second problem with the patch - this may well just be a memory thing again. Try applying all the above and remember to exit the game after you've changed all the settings for them to save properly, or else if it crashes you'll have to reapply the settings again! Then try patching and see if you get the same error.
Hope that helps!
On a sidenote, I'll agree with anyone who's had this trouble on a high-end machine - it is frustrating when you have a very high spec PC and can't play on the highest graphics settings, but think of it in the long run, this game will look better over the years
May your terror missions always be infested with Chrysalids.