Hi Dan. There are several things that make the device storage think it's so full that it has to snort out error messages. The best way to go is to take action in all of those areas as it is pretty simple:

- go into application manager and remove cache and data on the messaging
app as well as all social networking apps (Gmail, Facebook, Twitter, etc)

- power down and remove battery, SIM card and sd card momentarily then just put them all back in

- power up and reconfigure your apps

If all those actions don't resolve the issue, a factory data reset will (be sure to run a back up of everything you want to keep, first):

- in the phone app, dial 3845#* 970#