I use ssh with socks proxy: -D 1080

From some times I see a strange behavior with google services: it just
hangs my connection. It could be google.com, or blogger, or analytics.
(sometimes other sites, but it happens more frequently with google).
Th connection just hangs, no errors, and everything, even the ssh
connection itself is blocked.
Then, either one or more connection fails, and everything gets back normal.
If I want to regain connectivity, I could also close my browser (either
firefox or chrome)

I tcpdump'ed ssh server side, and saw nothing stranges, just packet
going through and never going back. I turn log on (-v) and nothing
strange too. I only have some "connection administratively prohibited"
but I'm used to see it and don't think there is more or less since the
problem arose.

My ssh conn is fine I can scp large file without problems, and my
connection from the sshd server to web is fine too. So, my question is,
how can I troubleshoot this problem, and how can I add more logs?

Thanks.
--
Kevin