This is my first post here. I had the same error before while trying to install the Nokia Maps update on my N800. After a few attempts with no success, I just went into the application manager and removed the previous version of Nokia Maps that was preinstalled on the OS2008 update and then I went back and installed the Nokia Maps update just fine. None of my downloaded maps were touched and I didn't see any problems.

Nokia should have noted on the installation details to just remove your old version of the maps program before installing the update.