Paypal Express taking me back to PayPal login after confirming order

I am using the latest version of ZenCart and we are processing payments through "PayPal Express Checkout". Some people have called this week saying that the site is not processing their orders. But we are receiving other orders through that module. We do not have any other Payment module installed.

I found that if I go through the following steps in checkout then the cart sends me back to my paypal profile page with my recent transactions and there is nothing listed.

1. click on a product
2. click add to cart
3. click login with PayPal
4. goes to paypal and has me log in
5. I log in
6. click continue (using PayPal Balence)
7. sends me back to shopping cart to select shipping
8. click continue
9. shows me total (step 2 of 3)
10. click continue
11. shows me step 3 of 3
12. click confirm
13. Sends me to paypal profile page with no recent transactions

but if I have IPN on and Express on then it works... I am confused....

Your first 12 steps make sense. But I can't get your step 13 to occur on a clean uncustomized install with only the Express Checkout payment module installed.

Could it be that I have IPN installed, but not active and Express installed and active?

I don't want to remove anything at the moment, but do you think if I uninstall IPN and just have Express installed and active that everything would be fine?

There's no good reason to use "both" the IPN/Standard module and the Express Checkout module at the same time.
And you shouldn't leave modules installed but set to "enabled=false".
Go to your admin, click on the IPN/Standard module, and click Remove.