here it is, vague but true.
You have a problem with "something" calling a table/Database bit of information that does not exist or is the wrong call.
What it is..who knows?
You have applied some mods and hacks to your site and one of them is causing the error. You also modified the theme, how much, we don't know that either. only you do. You need to look at what changes you have made and backtrack.
Start disabling Modules. Then start De-applying the hacks you installed, Script changes you've made, etc. etc.

That's all the help I can give.

mikem