Database questions - why don't my products show?

[tahiti amin]

Okay so I had someone redesign my website and asked if while they were at it they could update my version of zencart from 1.3.9 to 1.5.1. Well the updated the site and did not do enough troubleshooting before going live. Once the site was live my password and username no longer worked, but all my catalog items were still in place. I just couldn't log into the admin folder. After that I still can't figure out what the guy did but he pretty much just started deleting folders from my catalog. My admin folder was still there but if I tried to go to it I my browser would tell me the page didn't exist. Also all the catalog items were no longer there. IF I went to my database it still shows them and my site still retains the look that we had created so it has to be at least partially looking at my database right?
Anyways I took the backup of my site that I had on the my hardrive and installed it over the catalog which is already up on the server. I got my admin page back and I am able to log in but still no catalog items. I look at the configure files and they look fine plus I replaced them with the ones on my hardrive, which were from the working site. THis guy apparently did not know what he was doing but just kept moving forward anyways. I've taken over the work from there but I have no idea what he is done or how to remedy it. Has anyone had similar problems? Any ideas of where I should start looking for the fix. IF my database is there, and my configure files are pointing to it why would my catalog not be showing my items?

[kobra]

I took the backup of my site

Did this include a backup of the database before this happened??

[tahiti amin]

Okay so I had some people doing some work to my site and in the process I had them update my zencart. We had a backup catalog on the server for them to work on and make live when all the bugs were fixed. Well for whatever reason they took it live before such time and the entire weekend has been spent trying to get them to fix what they had broken. THey finally did a fresh install and now all my catalog items are there and the admin page is once again reachable but now when you go to checkout it leads you to a blank white page. I have attempted checkout using both the paypal standard and paypal express payment modules and both end with the same results. Any ideas to what might be creating this problem and how I can go about fixing it?

[kobra]

now when you go to checkout it leads you to a blank white page

I searched the faq's for "blank Page" and got this
http://www.zen-cart.com/content.php?...t-of-a-page%29