Connection lost

Hi!

Since I upgraded to v3.8, I get all the time this error message:

“Connection lost. Saving has been disabled until you’re reconnected. We’re backing up this post in your browser, just in case.”

Then the whole site freezes, I have to wait quite a bunch of time before connection comes back again. It happens so often that it blocks my whole work on my two wp websites: http://noubel.com (English) and http://noubel.fr (French).

I have checked many many posts about this issue. I did the following things:
* deactivating all plugins
* trying on other browsers (I currently use Chrome)
* clearing the browser cache
* checking the server activity

None of these worked. It has nothing to do with my bandwidth and connection. Not with my server too, as I can easily run other apps installed on it.

Reading many forums, I see people having this problem since they installed wp 3.6. it didn’t happen to me until 3.8, but it definitely seems to have something to do with an upgrade.

Any hints?

Thanks a lot!