When I have the USPS module enabled- I am getting the following error for shipping quotes:

We are unable to find a USPS shipping quote suitable for your mailing address and the shipping methods we typically use.
If you prefer to use USPS as your shipping method, please contact us for assistance.
(Please check that your Zip Code is entered correctly.)

It used to work properly. Also- when it was working, when I would advance to the checkout section- USPS was never offered as a shippng option- even though I was able ot get a shipping quote.

Right now though, I can;t even get a shipping quote..

Please help!