Don't know if anyone else is having problems using Google Map and Sprint Nav. I can't seem to get a GPS signal anymore.
My wife and I both have the phone, and it stopped about a couple weeks ago.
If you upgraded your phone to the Froyo 2.2 version, that's the problem. The same thing happened to me a few months ago, you'll have to go back to the old version. Here are the instructions I received from another forum: