John,
Thanks for the report. Not sure what happened, but it looks like LinkedIn changed something on their end that's breaking things. Their forums have a few posts with users having the same problem. We debugged it as best we could to provide all the information we could and posted it as well:
developer.linkedin.com/forum/oauth-callb...-point#comment-16216
Sorry for the inconvenience. Unfortunately, it doesn't look like there's anything we can do on our end, but we'll definitely keep an eye on their support area to see if there's anything that needs to be done.
Thanks, and keep us posted if the problem persists too long and you dont' hear from us!
Alex