A few glitches that have happened to me while playing Baldur's Gate that I remember, are these:
I had gone around to the back of the Friendly Arm Inn to get Joia's ring. After I had gotten it and brought it back to her, the surrounding area reset, after I had stepped out of her house. So, now I have her ring again, after I had already given it to her! But, she went away when I first gave it to her, and she will not come back, so I cannot get another reputation boost. Ah well, it's still interesting. I've kept the ring
This one is more funny then anything.
I was going around and looting all of the houses in Beregost. While I was in this one house, I had just stolen a dagger from a drawer. The second I clicked on the dagger to put it into my backpack Kivan says, "That was a noble deed." I couldn't stop laughing.