There appears to be some issue with my version of WordPress, the server in use and the version of PHP. The ISP recently upgraded my sever and migrated my site over to a new unit, which was supposed to be transparent. Right. I am working with the ISP to resolve these issues as quickly as possible and return to my regular blogging.
In the mean time:
Update: All fixed, for now anyway. Something about a mismatched password in the backend. To all those that tried to comment, my apologies. It should all be working correctly now.