Currently I am unable to log into the Management Section of my site if I select http://example.com/user. If I go to http://example.com/admin/reports/status I am then able to log in.
Now if I attempt to make any changes none of my changes are saved. Then if I attempt to add content it does not save.
If I look at my recent log entries I find "The directory sites/default/files/xmlsitemap is not writable, because it does not have the correct permissions set."
There is no xml file located in this directory.
My site has been up for about 2 years and I have had no problems

Comments

If all folder and file permisons on server are correct, it would be good to ask the host provider if they make some recent changes on their system. Not so long ago I stumble with some old sites for few days before asking and found that my host provider implement (not so successfully) new security policy that mess up things.

Entering The Dip and trying to win over it.