I am an ISV partner of SalesForce.com,
I use OAuth between my Google App Engine service and my service on Force.com platform to transfer data.
For some reason the handshake of OAuth needs to be repeated many times in-order for it to work.
The steps I take are: 1. Creating a RemoteAccess 2. Entering the consumer key + secret to my Google App Engine page. 3. Being forwarded to SalesForce.com to enter username+password.
And then, instead of being directed back to Google App Engine to finish the handshake I get "URL No Longer Exists" in SalesForce.com
Repeating this step a few times few hours later always solves the issue.
I wonder, does the remote access takes time to initialize? Did you encounter this issue?
Solution: SalesForce.com Set a Proper Message When Creating a Remote Access (here it is)