First Class Shipping error

[acharme]

I have hunted oscommerce and these forums.
I am running an unmodified oscmax 2.0 (latest download)
I have my country and postal code set in config/shipping
I have my address set for the shop in config/mystore.
I have a test product with .05 weight in the catalog (many of my products are only a couple of ounces.
Priority mail shows as $4.20 (mailed to the state next door)
Express shows as $18.80
UPS shows $9.32
First Class does not show at all unless I disable all USPS except First Class, and then it gives me this error:
-2147219434 - First Class mail must weigh 13 ounces or less.

So what do I need to configure (or re-configure)? Aaargh! I have tried everything that I can think of, and I am now officially stuck!

[acharme]

For those of you who would like the answer:
in my case, the setting that needed to be changed was in admin/configuration/shipping/packaging. It is the 'tare' weight that was putting an extra pound on my packages causing first class to freak out. I think the tare weight refers to the weight of the packaging materials...