Most likely problem (if you are using win98/ME): optipac devices are seen as mouse/mice 2 (or up).
Quick fix: enable "singlemouse" option (for games you don't need dual TBs/guns games, which might be all?).
If you want to use multiple mice devices at the same time (marble madness), or you have winXP, or above doesn't work, post that info and I'll see if I can help.