BT Voyager 2091 Signal Strength

[#1]

I have just bought a Dell M1530 Laptop with the Next-Gen Wireless-N Mini-Card installed  for wireless connection to my Voyager 2091 router, have set it up okay, if I am in the same room as my router it connects okay, however if I go to another room only feet away I cannot connect as no signal, but if I go next to the router it will connect and I can then walk to anywhere in the house and it will stay connected giving ‘very good’ to ‘Excellent’ signal strengths.
I can then disconnect & reconnect okay but if I shut down the laptop and reboot it will not find any signal until I go back to the router.
I have tried all 13 channel settings without success, also raised router as high as possible and even tried the half tin can around aerial, all without any change. 
Could I have a dodgy Wireless Adapter, aerial or Router, if so why does it show an excellent signal everywhere?
Any ideas anyone, do any of the security settings etc have any effect to the signal strength?

[#2]

I should get commission for this! Get netstumbler for free from http://www.netstumbler.com/ when you cant connect see if you can see the router with netstumbler this will also show noise etc which may give a clue.
You dont say which O/S. If the signal is strong then what error do you get when you try and connect?
It suggests that the problem is with the O/S thinking its not there or being slow passing the pass phrase. You could try without WEP etc and see if that solves it temp

[#3]

Thanks for your input samuria, I have had a very quick look at netstumbler and it says it is a tool for Windows that facilitates detection of Wireless LANs using the 802.11b, 802.11a and 802.11g WLAN standards, no mention of the N standard, however this may not be a problem as my router isn't N standard only the adapter is.
I have Vista on both my PC & Laptop, the signal only shows strong once I have connected adjacent to the router and then walked into other rooms, I can disconnect & reconnect away from the router okay until I reboot then it cannot find any signal or occasionally it will come up with an unrecognised signal, which I guess is because it cannot get the correct information from the router?
I have tried it without WEP etc but no difference.
I feel it is just a router range problem but cannot understand why a get excellent strength readings, can disconnect and reconnect away from the router until I reboot, what changes after a reboot?

[#4]

Did you try and see if netstumbler could connect tot it? I would think its more something to do with the network profile that it reverts back to when you reboot.  What profile is it using when you can connect? Is it using that profile when you cant connect?

[#5]

Tried netstumbler but it just tells me Access is denied, my Dell adapter card isn't on their support list, is this the reason?
Edit
Just read through the Netstumbler forums and see that it doesn't work well under Vista, which I have. 
Not sure what you mean by 'what Profile is it using to connect' ?
Where do I find the profile, is it only something I can see with Netstumbler?
I don't change any settings between when it connects and when it doesn't.
Don't forget I only have a problem reconnecting when away from the router and only after a reboot, no problems when next to the router even after a reboot.

[#6]

I dont use Vista so I cant give you exact instruction for your profile as I am going from memory. It sunder the network setup were you set the network to internet or local this sets  up what can and cant be visible.  I know when I have used it sometimes it makes one of the profiles default so if it gets it wrong next time you boot up the profile is set to no internet access.
What you are saying seems to indicate that this is were its getting its knickers in a twist and maybe looking down the Ethernet for the router.
someone using Vista may be able to give  clearer instructions

[#7]

Update

Problem sorted, spoke to Dell for nearly an hour going through all my laptop wireless settings, the most changes were made in the advanced settings of the Next-Gen Wireless-N Mini-Card.
It is a bit annoying that someone from Dell had to ring me to resolve the problem because there wasn’t enough information supplied or available about the various adapter card setting options that they provided.
I was about to replace my router or adapter card unnecessarily. 
Anyway it now boots up and finds the wireless connection immediately anywhere in the house. 
Thanks for your help Samuria.