I'm the latest to find a personal fix for this--although it was on a desktop, not a laptop. You'll just have to keep trying USB-to-Serial adapters until you find one that works. I was out on the ledge when the fourth one I tried worked.

There apparently is a difference between USB-to-Serial amd USB-to-PDA adapters, even though they look the same, so be careful. The three that apparently have solved most problems are the Keyspan US-19W (didn't work for me, although it has for many others), Belkin F5U103 (worked for me), and Xircom (currently unavailable). $49, $79, and ???, respectively. Go to the Keyspan website for that product. Belkin is available at major chains, such as Fry's and Best Buys. I assume go to their website if you're not domestic.

Good luck, it's a real pisser. I empathize completely.