Router admin help needed please?

[#1]

I've just ended one contract and started a new one at a new property and decided to keep the original Technicolor router as it is only just over a year old.  In anticipation of the new service being provided I decided to set up the old router with the new login details last night, but I can't log in 
The router fired up OK and I was able to connect to the wireless network easily enough and open the admin login page but it does NOT accept the serial number quoted on the bottom of the router.  I have NEVER been into the admin section previously as I have never needed to.  Does anyone have any suggestions please?

[#2]

..Only to check you are using the correct 'case' for the username and password (username is 'admin' in lower case if it's not been changed, password is upper case.)

[#3]

Thanks.  But I've already tried all combinations of upper and lower case. 

[#4]

If you haven't already , I'd suggest starting with a factory reset.

Quote

Use a paperclip, pen or pointed object to press into the reset pinhole on the back of the router. Keep the button pressed in for at least 7 seconds. When the power light goes red, release the button and wait until the power light turns green again. From this point on, your router will be restored to 'Factory Settings' so you'll need to start again from the beginning of this guide.

Then try to login with the serial number...

[#5]

Only do that with a wired connection as the wireless connection may be totally screwed

[#6]

Good point Jim, the wireless settings will revert to default as well. See here http://www.plus.net/support/broadband/hardware/technicolor-582n-faqs.shtml

[#7]

Thanks,  I was hoping to avoid the factory reset for exactly that reason - I didn't want to mess with the wireless settings.   I guess if no one else has any suggestions I might have to go down that route.
Interestingly the user guide for the TG582n states the following:-

Quote

The default user name is Administrator. The default password is either blank or the ACCESS KEY printed on the label of your Technicolor Gateway. This depends on the settings chosen by your Service Provider "Your system administrator may have disabled the physical reset button of the Technicolor Gateway. In this case, a hardware reset to defaults is not possible."

That could be fun 

[#8]

I've had problems in the past with TG582ns where in the access key an 'R' looked like an 'A' and a 'B' looked like an '8'.

[#9]

Unfortunately I have none of those in my Serial No#    But it was a good shout, thanks.

[#10]

The default user name is    admin    all lower case.

[#11]

Really weird this one.
I tried again last night, this time using my iPad and Safari browser whereas previously I was using my laptop and Chrome.  This time I was able to log in and make the changes straight away. 
The ONLY thing I can think is that the iPad had previously been connected to the router whilst it was connected to the old ADSL service.  It was therefore already in the WiFi device list so maybe it was "allowed" to connect to the admin interface?