No access / slow loading / timeout of Linkedin

I have been experiencing slow response (initially), and more recently, timeout while attempting to connect to Linkedin from home (Dell Inspiron 1420 running Ubuntu Hardy Heron 8.04, Firefox 3.1x or 3.5x, with D-Link 2640T ADSL/Wi-Fi combo modem/router. Apparently, there was no problem connecting with the office VPN, or through a proxy (e.g. www.tntproxy.com), but then Javascript is disabled with a proxy access --> I cannot update the profile or manage contacts.

I finally fixed the problem with the material discussed in:
http://marzoa.com/2009/03/08/d-link-dsl-g624t-and-linkedincom
https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/314713.

The ADSL default configuration for PPPoE is MTU (Maximum Transmission Unit) at 1400 and MRU (Maximum Receive Unit) at 1492. (I have Airtel 512 kbps DSL connection) Changing this to match the eth0 MTU default value of 1500 on the DSL modem did no good - apparently the modem cannot handle MTU = 1500. So, I tried the two steps to remove the iptables FORWARD and change the eth0 MTU:

(a) Delete the iptables rule as described from the router. I too had the offending line in position 1

iptables -D FORWARD 1

(b) Reset MTU on the machine (interface eth0 in my case)

sudo ifconfig eth0 MTU 1400

The MTU value is 1400 since TCPMSS is set to 1360 in the router. (Note: TCPMSS = 1400 - 40 = 1360)

Naturally, it is not a stable fix: I have to telnet to my modem, reset the iptables each time, but something is better than nothing... Next step: Try to upgrade router firmware and pray it does not screw things up any further ;-)