Add to cart from search page is broken

First let me say I'm a web novice and have relied heavily on the forums to work through most of my issues so a big thank you to everyone out there.

Unfortunately I can't seem to find a solution to my current problem. If I navigate through the menus to a product, then select a quantity it will add to the shopping cart just fine. However, if I search for a product (0-102 for example) and then try to add to cart it defaults me to the home page and does not add my product to my shopping cart. I'm not sure how long it has been like this I only recently noticed the issue.

I was in need of an update (I think I was running 1.3.9h) and to make sure I didn't take myself offline too long I had my host (Camelot) assist me with the upgrade. They seem quite a bit more knowledgeable than I am about Zencart so this seemed like a safe choice. I do not know if the problem is related to the update or not so I have not yet approached them with the issue.

I do have a template which could possibly be the issue but it has been several years so I don't have any idea where I got it. I also have a few add on's that I have listed below but it seems unlikely they would affect my cart in this manner.

I'm hoping this is something really simple and I can feel foolish for missing something so easy :)

Other info
MySQL 5.542-cll
Server: Apache

web address: http://www.paintsprayerparts.com/

Add On Items:
Ceon URI Mapping
Easy Populate 4
Image handler 4 (I think this is stock?)
And of course payment and shipping modules.

Thank you for any assistance you can offer.

Update: Found a work around. Set configuration > product listing > Display Multiple Product Qty Box to 0. Then the customer can still add the product to his shopping cart and just adjust the quantities there.

Thanks!

Did you happen to try the operation while the. Default template was temporarily active?

I just tried from a default ZC install to search for an item that came back with multiple results, filled in one of the text boxes selected add the selected item(s) to cart and was taken to the shopping cart with the quantity entered added...

So it may be template related, it may be the "upgrade" that was performed...

If you had:
Display Product Add to Cart Button: 1
Display Multiple Products Qty Box: 0

May want to try applying the patch here.

Otherwise can check if template (as mentioned by mc12345678) by temporarily switching to "classic" (the template example Zen Cart 1.5.x ships with).