Facebook and Gmail stop working after 10 minutes

Some troubleshooting ideas :

Start a terminal and run watch -d -n 20 dig www.facebook.com. Then, the moment that gmail or facebook shows the error, ALT-TAB to your terminal window and watch the next update for any changes. I'm guessing that these sites have load balancers in place that are changing the IP addresses behind the scenes. It's possible that your ISP is caching the content without your knowledge and your cookie is becoming invalid because the content being provided by your ISP is no longer a match for the connection being made by your browser.

You might be able to circumvent this by changing your DNS servers. Try right clicking on nm-applet, then choose "Edit Connections". Choose your ethernet connection (probably "auto eth0"), then "Edit". Go to the IPv4 settings and change "Automatic DHCP" to "Automatic DHCP (addresses only)".

All your going to change is the DNS entries - either use Google's entries (enter 8.8.8.8, 4.4.4.4), or OpenDNS (enter 208.67.222.222, 208.67.220.220)

I suppose the other option for possibly circumventing such a time-out is to run Gmail over https. Not sure if Facebook supports fully encrypted sessions. To set Gmail to use https, go to your account settings at the top-right of the page, then in the General tab, find the "Use HTTPS" option and select it.

I had a similar problem with Firefox. Even though I had IPV6 disabled on the system, I still had to disable it within Firefox.

I went to About:Config Entered IPV6 as the search term. Changed value for network.dns.disableIPv6 from false to true

I don't know if it will help you, but that worked for me.