Customer: "Can't get past step 3"

I am running

Zen Cart 1.3.7
Database Patch Level: 1.3.7
v1.3.7 [2007-05-23 02:11:05] (Fresh Installation)

And recently, customers have been telling me that they can't get past Step 3 in the order process, where they enter their CC information. The page just reloads and clears all the CC info when trying to move to step 4. It doesn't happen to every order but has been happening more recently.

The store is here:
http://thebudgetgraph.com/site/

thanks

What payment modules are you using? Has your hosting made any recent changes?

I am using paypal direct payment and paypal express checkout.

I can duplicate the problem since when I enter dummy info it just resets the CC information. Even when I have the paypal option ticked, it resets. I am not even sure how or why some customers can get through since I can't.

I am un aware of any hosting changes as well.

I really need help on this one.

First, try uninstalling and reinstall/reconfigure your PayPal module.