Cannot Access Secure Site

[#1]

Hi All PlusNet Forum
I am a newbie and relatively non technical who needs some help

I have a relatively new (3 months old) TP-Link router modem Model TD-W8960N. & a TP-Link network card
It is hard wired to my computer ie it is not used in wireless configuration
I am using Win XP SP3 upto date with Windows Service pack, Firefox (latest) IE 8 (latest) Google Chrome latest
Avast 5 Home A/V Online Armor free firewall (latest
Problem
I tried to connect to a secure site that I do not use very often http://www.alliancetrust.co.uk/ (a secure site) and after logging in correctly the page hangs and gives the following. (all my other secure sites work fine including banks)
"""""The Connection Was Reset
The connection to the server was reset while the page was loading
The site could be temporarily unavailable or too busy. Try again in a few moments
If you are unnable to load any pages, check your computers network connections
If your computer or network is protected by a firewall or proxy, make sure that firefox is permitted to access the web"""""""
I checked with Alliance Trust they say there is no problem at there end and no other reports of none access. They accept my login details are correct.  It was referred to their IT department and their comments were:
"""I have discussed with the IT department and they have advised me that
they have come across this problem in the past and it is to do with your
TPlink Router.
I would suggest you contact your Internet Service Provider and explain
the situation to them and they will be able to assist or provide and
alternative router.  Alternatively you could call the TPlink Support and
explaining that there is a particular secure site that you can't access
but you can access others, they should be able to offer advice.
Unfortunately this is the only thing the IT team can offer as the
Alliance Trust Websites are all up and running with no problems.
Kind Regards""""
I tried my laptop which has different software including firewall, and that did not access the Alliance Trust site either

I then tried accessing the site with a Voyager 205 ADSL modem and bingo no problem in accessing the site.
So what is causing the problem on this specific website & how do I sort it
Thank you
Terry

[#2]

I've seen similar issues before and its quite often the MTU setting on the router being too low.
Try setting the MTU to 1492. Sorry dont know how you do it on that particular router but its usually on something like the broadband link settings.
Hope that helps
Edit: Oh dear!, I've just downloaded the manual for your router and I can't see anywhere to change the MTU setting. Its got lots of other facilties like VPN tunnels etc but NO way to change the MTU!!!
Aah, a bit more googling shows that you're not the only person with an MTU problem on that router http://www.cybergamer.com.au/forums/thread/38849/tp-link-td-w8960n-issues/
See page 2 , looks like a firmware upgrade might help.
Try here http://www.tp-link.com/support/download.asp?a=1&m=TD-W8960N

[#3]

Hi Mr W
Thanks for your reply. I have today upgraded the firmware but it made no difference. TP-Link suggested dropping the MTU to 1460 (1480 is default) but that did not work either.
Would be interested:
a) in knowing why you suggest an increase as opposed to a decrease?
b) Any other ideas?
Thank you
Terry

[#4]

The Alliance Trust secure site seems to have a problem with its certificate.  Have you tried this:
https://atonline.alliancetrust.co.uk/atonline/login.jsp ?
Best wishes
Chris

[#5]

Sorry for not replying earlier , I didn't spot your post yesterday.

Quote

a) in knowing why you suggest an increase as opposed to a decrease?

If the MTU on the router is lower than that on your PC then the packet from the PC will get fragmented by the router, sometimes that will upset secure sites.
 

[#6]

Hi ChrisL
Thanks for your response. The url that you provide in your post is the one that "emerges" after www.alliancetrust.co.uk. In otherwords as soon as you click login you are taken to  https://atonline.alliance....co.uk/atonline/login.jsp ; ? and this is the url I cannot get past
Mr W
Thank you for that it was useful I did not know that.
I contacted PlusNet service to ask for their help. I was told that there was a lead time of 19 hours for a response, it actually took 53 hours to say NO WE WONT HELP YOU BECAUSE YOU DID NOT BUY THE EQUIPMENT FROM US!
They used the phrase we don't support the equipment. What they forget is that customers pay their subscriptions for broadband. I am NOT IMPRESSED with PlusNet.
Whatever happened to customer service.
Any other suggestions
Thank you
Terry

[#7]

Have a read of this, it might be of some help.