Checkout error after system crash

I recently tried to upgrade joomla 2.5 to 3 with disastrous results, site crashed and akeeba backup did not work. I ended up going to 3rd party ( cmshelplive.com/ ) and paid to have it restored to normal. It is now up and running ( www.honeyflowfarm.com ) but they are still working on a few problems.

Hikashop checkout has a problem and akeeba backup is not working. They can see the akeeba problem and are working on it, but they cannot duplicate the hikashop problem.

If I go to checkout, add address ok and then select "register" I get a:
"Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, This email address is being protected from spambots. You need JavaScript enabled to view it. and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."

I get this using chrome, firefox, IE and even my smart phone. My daughter tried from another state with same problem. BUT ONE ORDER DID GO THROUGH AND THE CMS GROUP COULD NOT DUPLICATE the prob lem???

I think the same thing may be messing up akeeba and hikashop.

Do you have any ideas that I could pass along to them? (They are a group that works with joomla and wordpress)