I used to be able to use button 3 on my old mouse, or "back" on my mx700 mouse to view all items on the ground,but since about a week ago I can't anymore.. the items just flash on the screen and disappear again. Has anybody else had this problem?

I might just reinstall d2, see if that fixes it :/

Never heard of that problem, but did this problem just happen once? I have weird things happen to me but when I re-boot D2 they go away, also maybe a program was doing this, check what was running and try shutting them down and seeing if that fixes?

It happened once, then fixed itself, then it happened again and has stayed happen. And nothing else is running, besides the essentials..

Erm, well not Diablo 2 for whatever reason happened to interprete not just button 3 but also button 4 and 5 if you have them as an [Alt] reaction which isn't so rare (do not know why this is, but its been in a couple other games as well that don't have explicite add-on for mouse buttons 3, 4 and 5.