I've been exploring the surrounding areas before going to the mines and when I try to get back at Nashkel, the game crashes one times out of three for no apparent reasons. I used to have the same problem with Planescape Torment, but I don't remember how I solved it.

By the way, does the Iron Plague (or whatever that is) also affects magical weapons (like +1 weapons)? Can I use those, or do I have to stock on quarterstaves?

No magical weapons are not affected, they won't break.

Do you have any of the fix packs installed? Having said that, if you had the same problem with P.T. it may be your rig or some other issue at fault. As already stated, magical weapons are unaffected.

I did have all the fix packs installed. I remember something about emptying a temporary folder could fix the crashes, but I can't remember which folder.

While the game is running, BG maintains a temporary store for some of it's assets, especially area (.are) files. These are usually cleaned out when you quit the game. Make sure that the game is NOT running, and check in your BG installation folder. There will be 2 folders called 'temp' and 'tempsave'. Delete anything in them, but only when the game is NOT running.

Well, the folder was full. Now that I emptied it, it has stop crashing.

If only I knew why it crashed in the first place, but now it works. Thanks.

If it was full, then there were left over area files that should not have been there, and those were conflicting with what was actually in your game.