434 seems to be a step down, in terms of stability.
While playing in ZC, it crashed seemingly randomly, although of the three times I saw it, each time I was pressing L or R (buttons 5 & 6 on my game pad) when it happened.
I tried this in 1st.qst, and in Zodiac, but in the former case, I didn't have any weapons to switch, and in the latter, the L and R buttons are rescripted. In both cases, hitting L and R don't cause a crash. However, in my game, hitting L and R does cause a switch, and does cause a crash sometimes.
http://zctut.com/mike.zip (it's uploading now, will be up in a minute)