It's a problem with the most recent update. I get the same msg when posting, even though the post does go through (albeit delayed). I've also noticed that even though the app will show that I have notifications, the drop down to actually show what the notifications are never updates. These are new issues that began on my phone (Samsung Galaxy S3) after the most recent FB update.
Since I don't know of any way to go back to the previous version (anyone? Lil' help!?!), your only recourse is to wait for a new update that might fix it or go to FB mobile on the browser.