Jason, that error appears to be due to an emergent issue at PayPal's end, which they just confirmed to us when we inquired with them about it today, so now we're just waiting on them to fix it.
This issue only seems to affect sellers using PayPal Payments Pro when the buyer chooses the PayPal checkout button in your cart; I've asked our PayPal tech contact to confirm this, but so far only PayPal Pro merchants have reported a problem to us today, and PayPal Payments Standard seems to work fine when I test it.
If so, a temporary workaround could be to disable PayPal Pro in your E-junkie Profile -- just select My payment processor will charge cards for me in the Accept Credit Cards section at Seller Admin > Manage Seller Account > Edit Profile. This should allow buyers to checkout with PayPal, though it would also remove the Pay With Card checkout button in your cart, so it's your call whether this is worth that tradeoff. Once PayPal resolves the issue, you can simply re-enable PayPal Payments Pro in your E-junkie Profile.