I'm in Iran and having the same problem in this week but only one or two hour at nights !
i've changed my dns from 8.8.8.8 to 4.2.2.2 and it was better.
it's not for mail.google.com and even plus.google.com.
it's only for google.com and because of google reader (since its forbidden in Iran !!!)
i think they are trying to filter google.com/reader (as in is with http, but via https it works.)
there is a invalid certificate error and sometimes timed out