From the two errors you've provided, I can't come up with much. However, I wanted to make sure you haven't overlooked the answer.
My suggestion to you is to look at the page below and see if any of the situations given at the link below may apply to your scenario:
See this page on the Facebook Developer site
Here is an excerpt regarding the second error:
"Facebook doesn't notify you that a previously issued access token has become invalid. Unless you have persisted the expiry time passed to your App along with the access token, your app may only learn that a given token has become invalid is when you attempt to make a request to the API."