I was having a problem where Wordpress post drafts on my main blog were not saving. I would press the schedule/publish/update button when I was in the HTML view mode (the default mode that I edit in), and the text would change from a monospaced font to a non-monospaced font. Nothing would happen otherwise. I would press the button again, and all of the text would completely disappear, and my work would be lost. Nothing would save to the database. I had to go into the quick edit mode on the all posts page to actually edit anything. Clearly this was unacceptable.
Here are the steps I took to fix it:
Ensure I was running the latest version of Wordpress (I was)
Ensure that all of the plugins that I had were completely up to date
Disable any new or flaky plugins, or those dealing with editing that might have caused the problem
Somehow proofreading got turned on, and this seemed to cause problems. See here to turn off Wordpress proofreading.
After doing that, things seemed to work much better on the saving front.