Live Magento Site - Googlebot etc show 500 internal error

Avg Bid (USD)
Project Budget (USD)
$30 - $250

Project Description:
For some reason starting on saturday googlebot can no longer index our site, w3, also show 500 internal server error but the site navigates just fine. I cannot seem to figure out what is wrong..

Looking for an urgent solution (within hours if possible) our site is live and down time isn't an option.

Skills required:
Magento, MySQL, PHP
About the employer:
Public Clarification Board
Bids are hidden by the project creator. Log in as the employer to view bids or to bid on this project.
You will not be able to bid on this project if you are not qualified in one of the job categories. To see your qualifications click here.

$ 78
in 1 days
$ 206
in 3 days
$ 100
in 1 days
$ 257
in 3 days
$ 83
in 3 days
Hire iclicknetwork
$ 147
in 1 days
Hire linuxfreak1985
$ 309
in 5 days
$ 144
in 3 days
$ 53
in 0 days
$ 206
in 13 days