Possible solution:

Possibly related to couple of backup recent restores I found I was getting "device memory full" trying to save or change contact or sharing accounts.

[Unrelated, but this was in the course of trying to resolve some probably inaccurate "application memory full" errors]

I was preparing to reflash and removed the battery to get the device serial number... this mean I had to reset the date and time stuff and ... the 'device memory' issue was resolved.

So... a few seconds with the battery out may help.