Messages.app for Mac Yosemite version deleting all messages after warning of Full Hard Drive

My MBA 13" Mid 2011 is having trouble with Messages.app. All was well until I got a warning this afternoon that my Hard Drive was nearly full and I might start to lose new incoming messages.

I cleaned up some space and turned this checkbox back on (it had been turned off):

Nevertheless, my messages app has retained only the conversatoin threads.. all messages disappear moments after being sent or received. Sent messages hang forever in the sending state (do not say Delivered on iPhone) but in fact they are sending. I can also receive and briefly read incoming imessages (and I believe sms).

Here's some Console logs that might be of help.

9/28/15 01:51:16.240 IMRemoteURLConnectionAgent[1622]: SACShieldWindowShowing:925: ERROR: NULL response

9/28/15 01:51:16.633 imagent[1337]: [Warning] Attempted to create IMMessageItem from NULL IMDMessageRecordRef.

9/28/15 01:51:16.661 soagent[1349]: Can't allocate SOHelper <SOMessageHelper: 0x7fe1REDACTED> inside com.apple.soagent

9/28/15 01:51:20.683 com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.

9/28/15 01:51:20.768 Messages[1625]: schema version 4294REDACTED

The computer still seems to know its own serial number. Had read that's a common enough problem.

Any idea?