I doubt very seriously that it’s a theme bug, or more of us would have this problem. This is most likely the result of a bad plugin, edits made to WordPress or Graphene core files, a malicious hack, or poor security on the part of your host.
You should be sure to read this page in the Codex:
http://codex.wordpress.org/Hardening_WordPress
Make sure that you are only using WordPress core, themes, or plugins that you get from WordPress itself. You can’t make any guarantees about things you get from other sites, even if you pay for them.