If you’re on a shared server, then another user on that server may have reached the geocoding limit. There’s some information about this problem in the documentation and the FAQ.
I was about to tell you you’re out of luck with that server, but I just checked Google’s docs and they seem to have changed their rules.
Previously the geocoder didn’t even accept an API key. The key only affected the number of maps that could be displayed. However, at some point this must have changed. The geocoder now seems to support API keys, which would imply that you could get a ‘private’ 2500-request limit.
I’ve updated MapPress to pass the API key to the geocoder, and it seems to work. Please send me an email and I’ll send you a copy of the updated code to test.