A quicker key combo to save is Ctrl + S.

There is no keyboard shortcut that changes a document to read only. Are you on a network?

Check your settings in Tools/Options/Save. Do you have Read Only Recommended checked?

Are you saving open files directly to disk? This will change the attribute to read only.

Have you recently had a crash? Do a search for all temp files and delete them. Search for the following:

*.tmp, ~*

.