What does this mean and how do I fix it? :(

dWhen ever I check out through my shops express paypal option I get this error

http://home.btconnect.com/dreadfallhair/scrnshot.JPG

I am using 1.3.8a and have uploaded the payments mods that I downloaded from this site, through the FTP so I would be guessing they are the latest version.

I just cannot for the life of me figure out whats wrong so please help me?

If you're using Zen Cart 1.3.8a, you would have had no need to download Paypal Express as it's built-in. If you did download it, it would be for an older version of Zen Cart and likely incompatible, with the current version. The error that you're seeing could well be a symptom of this.

I meant I downloaded the WHOLE install for zencart and re uploaded the paypal modules because I saw on here somewhere that the old version might be the problem, so I thought I would double check but it still isn't working

zen_order_id is used by the older versions of the paypal mods. It's not used by the the current versions. The code that is failing doesn't exist in the current versions. Somehow, you must still be uploading older versions, and over-writing the ones designed especially for Zen Cart 1.3.8a.

Oh grr.
The only ones I've been uploading are the ones in includes\modules\payment\paypal. Is there perhaps others ones that may be the old version...