I'm facing a strange issue with all versions of wordpress starting from 3.2.1 upto 3.5
The "Link to Existing Content", "Choose from Most Used Tags" and autosave functionality stops working after few hours of upgrade to new version.
I've tried everything what Esmi has told in other posts like
1) Resetting all Plugins using PhpMyAdmin, Renaming Plugin folder to Plugin.hold and keeping all plugins deactivated
2) Switching to Twenty Elevan theme
3) Deleting wp-admin and wp-includes folder along with other files and re-installing them
4) Deleting browser cache and changing browsers
5) Deleting temp files
6) Optimizing MySQL tables
7) Disabled all browser plugins, add-ons
but still the issue crops up after few hours of new install/upgrade.