Patrick, thanks for the response. I had already googled that, and several other things looking for some low hanging fruit.
The thing is, the code being used is in Bullhorns jar so I don't have any code to provide, the extent of our code is to invoke a method in the jar (passing in credentials)
The error appears to be something from the Bullhorn rest client itself, which is generated trying to parse the results returned from the API during oauth2 negotiation. But since this is a BH provided jar, and the error appears to be between that jar and the BH API there isn't a lot more I can provide.