Only for those who have problems with upgrading to Mapsource 6.15.3 under Windows XP
After upgrade to 6.15.3 I ran into a run time error when I started Mapsource.
What helped was the following:
Take the normal precautions:
make a system restore point
Open the Registry with Regedit (under run==> cmd ==> regedit)
make a copy of the Registry in a folder like My Documents (File ==> Export).
look under HKEY_LOCAL_MACHINE
delete all OSM based maps under Products map
Close the editor
After this restart Mapsource
re-install the (new) OSM maps
and it should work.
It is a bit a dangerous process, but in my case it worked on 2 computers and without the need for a re-installation of the old registry.