So, the title says it. However I can build or break when about 15 squares away from my base (I am in a server). Server has been restarted, to no avail. Various other things have been tried. Any thoughts?
There is a protected area around a server spawn, to prevent players griefing the place where everyone spawns in. Move away from that area, or ask the server owner to change the protection radius (requires editing server.properties and a restart).
Normally all Minecraft servers will have this enabled by default.