Hi groversdad,
Welcome to Laptop GPS World.
* No need to reinstall Microsoft Streets and Trips, or Microsoft AutoRoute. Any problem with S&T Keys (or AR Keys), is directly related to S&T Keys (or AR Keys), and it is highly unlikely related to any issue with Streets & Trips, or AutoRoute.
* I think the problem may stem from the fact that I didn't think many people would want to run 2007 version of one product, and 2008 version of another product. But since Microsoft never released AutoRoute 2008, you have no choice but to run AutoRoute 2007 - and here comes the problem with my Keys .
* I suspect you could "fix" the problem (at least temporarily - till your next trip to EU or NA), by removing the keys.ini file located in C:\Documents and Settings\YourName\keys.ini (or a similar location).
That file contains also your Home and Favorite locations, so I'd suggest not to delete it, but only rename it, or move it to another location temporarily.
The next time you run AR Keys, it will create it's own keys.ini with proper values.
After using Microsoft AutoRoute 2007 in Europe, upon your arrival to North America, remove/delete/or rename the keys.ini file again, before you run Microsoft Streets and Trips 2008.
Let me know if this helps.