To save memory on the card, I had only downloaded 1 or 2 local maps - to leave enough room for Northern France etc. When I returned, and used tha unit locally it turned out that the new routes I had created, had gone off the downloaded maps. If the 2610 has a "simulate route" option, try that first as I wouldn't be suprised that you find that the route you have selected, has taken you off the downloaded maps. Either that, or for some reason the relevant map hasn't been downloaded. I just used the "Select maps around route" option and I've neven seen that message again. Hope that is some help.
this seems to have been the problem. not sure why, but it's working now.
new map set downloaded in the prescence of personal gps guru & it seems ok.
didn't do anything different AFAICT. now i know how it feels when i do something on other peoples computers & when it works they start wailing "but i've already tried that & it didn't work"