I uninstalled the app and then installed it again and all was fine, after sending a few messages the same error occurred again. I have now found that if I clear data in the app settings it will connect again, once I have reconfigured the app and restored from backup. I can only assume that there is some sort of buffer which I am clearing as I lose a few messages when I clear data (all since last backup).
Barring doing a delete of all backups and messages does anyone have any other idea. I have looked and the backup files are about 1.7mb so not massive and I have a fair bit of storage available onboard (>7gb).
I was talking to someone with a HTC phone who had suffered similar symptoms but I have googled and searched and can't find a solution.
Any help much appreciated.