I didn't mean to cause difficulty either.
However I DID STATE that I was using the SAME VERSION and that the suggested fix did not help. I then pointed out that the issues seem to have arisen for me as well after the upgrade to 3.5.1.
As for a suggested fix other than going back a version I have not found one yet.
Therefore my problem IS IDENTICAL to tlkuhn's. Sorry if I insulted your response but it was incorrect (though an obviously good try)...
Again, deactivating all plugins makes no difference and multiple sites would not all fail in an identical manner if the plugins are not at fault.
I will suggest a caching plugin may help speed things up but this does seem to be a difficulty with the new release version.
Perhaps another suggestion esmi? I know I would love a solution as well.