Sandbox OAuth token-request changes?

[RJ at Kabbage]

Dear Etsy (and/or other knowledgeable people):

As of yesterday (5/1/2012) around 1pm EST, OAuth started failing for our app in the sandbox environment only -- production still works. Below is a copy of the request for the token, which is currently getting HTTP 500 in response. I've redacted the crypto-looking parts, because I'm not sure which ones are sensitive. Any help you can provide would be excellent! Let me know if you need more info.

GET http://sandbox.openapi.etsy.com/v2/oauth/request_token?scope=email_r+listings_r+profile_r+transactions_r HTTP/1.1

Authorization: OAuth oauth_callback="https%3A%2F%2Fservices-local.kabbage.com%2Fbounce%2Fend",oauth_consumer_key="(redacted)",oauth_nonce="(redacted)",oauth_signature_method="HMAC-SHA1",oauth_signature="(redacted)",oauth_version="1.0",oauth_timestamp="1335970596"

User-Agent: DotNetOpenAuth/3.4.7.11121

Host: sandbox.openapi.etsy.com