Upgraded to 3.95

Upgraded DNN to 5.6

The shipping is so frazzled I don't even know where to begin. The only way I can get the shipping to show up on the order page is to use Custom Shipping with Fixed Amounts..

Example of problem:

Add a product to cart.

I have 3 shipping methods to choose from, and each one matches all the proper critera, no currency symbols, etc.

When selecting two out of three (The bottom and top one) it throws me back to the home page and gives me the famous "A critical error has occurred.
Input string was not in a correct format."

I've deleted, recreated, etc. This problem didn't exist before. Prior to the upgrade, the combine shipping didn't work. After the upgrade the combine shipping check marked remained checked, but the mentioned problems occured.

Everything is tested and verified.. DNN installation, no errors, clean upgrade. Newest version of the cart, etc.

I can't even use the other shipping methods.. like by amount, etc. I can't take advantage of:

"Pickup in store, deliver, etc."

The absolute only way to get Custom Shipping Methods to even be valid and show up is by using "Fixed Amounts with combined shipping checked" and they still dont' work correctly when clicked on.

I'm not sure what the difference could possibly be between my hosting environment and the testing site here...

Is anyone else having this problem or found a solution?

Patrick