I've been having a very strange problem over the past few months:
After about 2 days of uptime, suddenly my computer can't connect to any google.com servers on port 80.
It doesn't matter what browser I'm using, even telnet to port 80 doesn't work.
ping works just fine as does nslookup so this isn't a DNS problem.
The computer is connected via ethernet cable to a router, other computers on the network don't have any problems.
Taking out the cable and reconnecting it does not help, and neither does ifconfig eth0 down or restarting the network services.
Only solution so far is to restart the computer.
I found another thread with someone who had the exact same problem, unfortunately it does not end with a solution:
If anyone has any idea what else might work I'd be happy to try, this is starting to drive me crazy.