There is only so much gold/diamonds/other ores in a chunk. Run until you think you have past a few chunks, and start mining. This should solve your problem.
I'd almost rather start from scratch.
Hey guys, we had some 'complications' last night with the members. Something weird is going on where when you are building something, a radius comes around it where you can't build. I plan to contact the host.
I've decided to put a whitelist on the server. If you wanna play, PM me your Minecraft name and I'll add you.
Here is the IP: sc36.servercraft.co:6663
Also, the server is up 24/7.