Let me see if I can help in some way. I wasn't able to install from my CD, but was able to install from the image on the TomTom site. I understand your frustration, but you'll be rewarded once it's set up. I'm using Missing Sync and TomTom without a problem.
I'd suggest deleting what TomTom files you have currently on your Treo and start from scratch. Use the latest image from the TomTom site to install the application. I installed mine on the SD card, but that's your option. I used this
image (Control-click and save to desktop) to install and it worked great. It's up to you if you want to try that route. If I recall, it "knows" that Missing Sync handles the HotSync and places the app there for install. Once installed, I would use the same installer for maps (with the CD inserted). I installed Canada and the New England Maps. They do take quite a bit of time to install, but you only have to do it once. You cannot and should not uncompress the CAB files. I would try installing your primary map and go about the activation procedure. No sense waiting through two map installations if it's not going to find them.
You can view/change your maps by going into Preferences > Right Arrow > Manage Maps.
The one thing I found when installing TomTom was that the order of the process made a big difference.
-Chris