Edit timestamp

Hi
What Causes the Edit Timestamp? In the post edit window the Schedule Button and the add tag button do not work?
I have deactived the plugins and everything works, I active plugins one by one but it is hard to see if a plugin is causing the problem because
it does not seem to matter because its a different plugin each time.
I have 3 other sites all with the same plugins and same theme and they all work find one other thing the file permissions in the public_html folder on the web server of the troubled site keeps changing to 750.
Any information would help grately.
Thanks in advance
Bruce