Cannot post

The system will not let me post anything in reply to one of my posts:

Correct the highlighted errors and try again. Post flooding detected (community received posts of a unique message more than 1 times within 3,600 seconds)

And when I tried to message the person who I wanted to reply to, I get an error message that I had reached my limit of private messages though that is the only one I have ever sent. What's happening here?