500 Error with FEDEX Automated Shipping Labels

I've just installed this plugin Fedex Automated Shipping Labels (1.2.0), and when I click on the "Ship" button from the Orders Admin page I get a 500 Server error. When it tries to pull up this page: ship_fedex.php?oID=698&action=new&status=3.

Currently my Zencart environment is version 1.3.8a, running in IIS 6.0 with PHP 5.2.12.

I don't think any of my files are custom that this plugin requires to edit. I followed the "merging_instructions.txt" very closely, when I saw the 500 error I figured I probably did something wrong, so this time I just copied over the files in the patched_core_files directory.

One thing that is different, is I've renamed my admin directory to something unique (as suggested Best Practices), so I didn't upload anything to my /admin directory (instead to my unique directory).

I tried enabling debugging and I don't see any log files anywhere. I do have the FEDEX shipping modules working receiving quotes, both plugins are pointing to the production environment. I entered my account number, and tried entering my meter ID for both the group service and express service (from the other plugin). Neither of these worked... I'm wondering if "FEDEX ACCOUNT METER" is not the meter id, and I'm entering something wrong?

If anyone has any ideas it would be really helpful.

Thanks in advance!

Just to add a little more info, I tried the page off the Super Orders as well and I get the same thing.

Here are the settings I have (with a few things censored)

Debug Mode false
Server production
Last Shipment Time 17
Email On Shipping true
Thermal Printing label
Fedex Account Number #######
Fedex Test Account Number
Fedex Account Meter ########
Company Name ##############
Contact Name ##############
Address Line 1 ##############
Address Line 2 NONE
City #############
State ##
Postal Code #########
Phone Number ##########
Currency CAD
Shipping Weight Type KGS
Default Package Type Your Packaging
Default Dropoff Type Regular pickup
Label Resolution 192
FedEx Express Saver true
FedEx Priority Overnight true
FedEx 2day true
FedEx Standard Overnight true
FedEx First Overnight true
FedEx Ground Service true
FedEx Home Delivery true
Cancelled Status Processing [2]
Shipped Status Shipped [3]

This is FedexAl. I just checked into your technical concerns, and it was brought to my attention that "usually the 500 error code means that the browser is not communicating with the server or visa versa, so the customer needs to clear their cache (temp files) and cookies and then bring a whole new browser & try it again." If you have any further questions on this, you can contact our technical support department at (877) 339-2774.