ssh issue in fedora

[zeusys]

Hi
I want to use ssh as a secure tunnel to browse filtered sites in my country,like facebook.
This ssh account works perfectly in windows with putty.
I'm using this command in linux to establish ssh connection :

ssh -D 3456 username@ssh_server_ip_address

At first , I can browse websites through this ssh tunnel.After spending 2-3 minutes, I can't browse any website anymore.It seems something cause ssh to stop sending/receiving data.

I did a test with VMware workstation.I installed Fedora 14 as a virtual mashine on vmware workstation and set its Network adapter type to NAT.VMware WS NAT' IP range is : 192.168.153.X . My real network IP range is 192.168.1.X which provided by a DSL Modem dchp enabled.In this case , by this virtual fedora machine I can use ssh and it works perfect without any stop in sending/receiving.

But I want to use this ssh account with my real OS ,not the virtual one.
Please guide me if anyone have any ideas

Thank you

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CPU : Intel Q9550
MB : Asus P5K-L Deluxe WiFi AP
RAM : 4 GB
OS : Fedora 14
Connection Type : ADSL2+(PPPoE over Ethernet)