help w/ wireless

Hi I have a  new Dell Inspiron B130, wireless card 1370. Dell has sent me a second computer as the antenna has crashed. I think this one went out today as well My wireless router is a new Att 2 wire 2701 series. They as well sent me a new router as the original I just got when I bought my father this computer. It was a 2wire 2700. The problem I have been having is my speed jumps from 54mbs down to a slow 1.0. I have played with the settings on the routers and the power settings as well. I currently have them set at wireless channel 9 and power setting 9. I had the channel set at 11 and the power was still at 9.Then I changed it today to channel 10 and kept the power setting at 9. The tech changed the channel to 9 and the card could not locate any router including my own. Then it located it and it would not connect to the internet. 

 Today the four "Cingular Raise" the bars located in my system tray started to go from green to yellow to blue and back to green, then the speed started to drop to 36mbs then i called ATT and they told me to call dell to change the wireless card power setting to match my router. I  called dell and the tech said there was no such thing then she did all of these changes to my card and it just got worse. She had me update the driver and then I  eventually had to do a system restore. I am wondering if anybody knows if there is a conflict with the wlan 1370 card and 2 wire? I have moved the router to the living room with NO electrical interference as there is nothing in the room but a sofa and the coffee table. I also have a whole house filter put on at the phone box outside my house wired into the garage down the basement and into the jack that the router is at.
I have two other dell Inspirons 600m's and have had no problems. No dropped signals and no dropping of speed?

The first Inspiron b130 computer had the same issues. It would find the signal 1 day then it wouldn't. They then replaced the wireless card but it did not resolve the issue so they sent me another computer that i am on now. And guess what I believe it is a atenna issue. 

They want me to go to a hotspot tomorrow and see if I can go online. I know if I try to go on my neiborghs i have little speed whereas if I am with the 600m and in the same location no problem?