I spent about 5 hours researching, downloading, installing and rebooting last night, but eventually got my 8100 to work with my ThinkPad T43 as a modem. I have noticed questions posted about these errors, but haven't seen any answers, so I thought I'd post what I did in case it might help someone else.

The 720 solution may only be for, and work on, ThinkPads. This is because I noticed that almost everyone who had a 720 error was using a ThinkPad and read posts indicating that it was possible that some of the IBM ThinkVantage software was responsible for generating the error. The 732 solution might work for anyone, and might not even be a solution - I accidentally happened on something that worked, so I went with it. Thoughts and feedback welcome.

The steps are easy, but long. The first thing I did was to remove the BlackBerry Desktop Manager from my computer and delete the special BlackBerry connection I had set up in Network Connections and remove the special TMO-specific string from the modem entry in Phones and Modems (NOTE: If you remove the BB software first, it will remove the modem from the computer and you won't have to do that last step).

After all BB stuff was removed from my computer, I rad IBM's Software Update Utility. I hate this utility, it inevitably makes matters worse, but I was at wit's end and so ran it. It turned out that the utility said I had a whole lot of updates to perform. I performed every update that it mentioned, which included updates to my modem, my ethernet card, my security softare... even my DVD player. I downloaded and ran them all. It took a long time. To make matters worse, the buggy update utility kept on saying I hadn't installed some of them. It took me actually installing each package, one at a time, rebooting after each installation, before the Software Update utility agreed that I had installed everything. (NOTE: I actually did a complete cold boot for some packages, particularly the ones that made a hardware change. This took a lot of time, but I wanted to make sure I covered everything).

I then ran the System Update utility, which actually found 3 more things that my computer needed. I downloaded and installed those and rebooted.

After IBM stopped telling me I needed to update something (running both Software Update and System Update came back null) I reinstalled the BB Desktop Manager FROM THE DISK THAT CAME WITH THE PHONE. I have no idea why, but it seems that there are differences (real or imagined) between the DM software at the my.t-mobile.com site and the disk. Everything I read said used the disk, so I did. I then rebooted.

Only then did I set up the modem as a network connection using the instructions earlier in this thread. After I set up the network connection I added the TMO string to the Standard Modem (COM4) that represented the BB. I then ran the connection and voila! no more Error 720.

One problem. I got an Error 732. This actually was more promising to me because it was a PPP error which I felt could be resolved through some software settings tweaking. Unfortunately, I couldn't find any info on how to make those changes, or what changes to make, on this board or elsewhere. This was frustrating. I kept on trying the connection, with no username and no password as indicated in this thread and elsewhere (for some reason every time I launched the connection it put my XP username in the username field - I deleted it so that the field was blank), and kept getting the Error 732.

Finally I got so frustrated that I accidentally hit the [ENTER] key instead of the backspace key when I went to remove my XP username from the username field. Amazingly, the connection worked - no more Error 732. I tested the connection and was able to surf. Just to make sure, I disconnected the connection and tried again. I launched the network connection, made sure my XP username was in the username field with the password blank, and it worked again.

I have no idea why, but it seems that the connection required something in the username field, and it may specifically have required my XP account username. I'm not sure, but it works and I'm happy.

And that's my amazingly long solution. I hope it works for you. It requires patience and time, but you'll be happy with the results if it works. It's better than some of the more draconian measures I've seen others take, like formatting their HD or reinstalling Windows.

One last note, make sure any other connection you have going is disconnected when you try to use the BB. I have wireless in my house and made sure I wasn't connected to my home network before trying the 8100 connection. This may or may not be critical, but it was what I did and it may work for you.

If you have any questions, feel free to PM me.

Stu