Laptop + Squeezebox having problems with new router

Hi all.

I recently upgraded my old Linksys WAG354G router to a Netgear DG834GT because the Linksys was getting old, making a loud electrical noise and started getting very hot.
The Netgear DG834GT is running the DGTeam firmware (V1.02.16 - DGTeam Rev. 0847).

For some reason my brothers laptop and Squeezebox, which is only about 4-5 meters from the router, seems to have really poor wireless signal. His laptop seems to fluctuate from very good to low signal in a matter of seconds for no reason. His Squeezebox is even worse and actually loses connection to the router completely at times, which is incredibly annoying when listening to music.

It's strange because my dad's laptop has excellent signal throughout the entire house and I can use it right up the end of the garden (50 meters or so!) where it still has good signal.
I don't understand why it's only my brothers laptop and Squeezebox that is having problems.

Why could this be?
The laptop and Sqeezebox is only ~ 5 meters from the router.

If the wireless mode is set to something other than B&G, try the B&G only setting.

I had a problem with a G device and a N Linksys router until I turned off the N and made it B&G in the router. Range doubled for me.