Logged out immediately after logging in when trying to send message.

This has happened to me a few times, but I can't quite figure out how to trigger it. I goto crusher, login, click to my event, click to send an announcement, write my message, hit send, and I get redirected to the login page and my message is lost. This all happens in about 5 minutes, so I don't think my session should time-out after that short of time.