Every now and then it seems that my Droid doesn't want to get a GPS lock. Most of the time it does really nicely, but sometimes it won't get a fix at all.
When I use GPS Status to see exactly what's going on with it it will generally show several satellites, but no fix on them.
Sometimes if you leave it running for a while it will eventually get a fix, but not always a good one.
I'm not sure why this functionality seems to come and go, but it gets quite irritating.