Saving causes server not to respond
The first thing I would try is to "Disable" every single one of your plugins. If that solves the problem, go through and re-"Enable" each one of them until you have pinpointed which plugin is causing the problem.

If that doesn't help at all, the next thing I'd do is to open up the Craft logs, and see if anything suspicious is in there...

/craft/storage/runtime/logs/


And if you're still not seeing anything noteworthy, then it might be worth submitting a ticket from the "Get Help" widget on your dashboard. Be sure to include your logs, database export, and files.