Seems to be the same problem described here.
Idem, when trying to Save and Publish a php error 414 message appears. It happens in Firefox, Chrom and IE, no other prowsers tryied.
Firstly, please deactivate all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one and let us know if you find the problematic plugin(s). Maybe there is a conflict in plugins.
If you still face there issue, you can send me username & password of your site for further checking (via private answer).
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