After getting a few new bits and parts, I came up with a much more reliable bumper system... Instead of the overly-complicated spring/hinge mechanism, I converted it to a simple stip of aluminum bent at the ends and near the center. It's simple and works better! The pics of the bumper are on the bot's site at http://www.gear21.com/scook/bot/.
Some of you may have noticed that if it runs into something in the middle, it won't set off the left or right switch... but that's why I have the GP2D12 IR range module *GRIN*.