Wi-Fi became incredibly slow

Question

I have a MacBook Pro late 2009 model, TimeCapsule 500Gb(1st generation) and HP Pavilion dv6laptop with 802.11n networking.
MacBook Pro has a Windows 7 SP1 installed on a BootCamp.
TimeCapsule is configured as 802.11n (b/g compatible).
Yesterday I turned on my Mac and found that the wireless signal is incredibly poor.
Same was from BootCamp's Windows side.The signal is almost absent, so mynetworking is almost impossible from the laptop if I use Wi-Fi connection.
Then I plugged-in a network cable to a Mac and found that the speedis excellent, like it was a day before yesterday on my Wi-Fi connection.
Afterwards I turned on my HP laptop as usual and found that Wi-Fi works greatand operates on its usual 802.11n's speeds!
I also have an iPhone and I found that its Wi-Fi is also incredibly slow - same as on a mac! But ina restraurant my Wi-Fi on a phone is excellent.
I tried reseting NVRAM on a laptop, re-installed 10.6.6 Combo Update, rebooted TimeCapsule - nothing helps.
Dear community, please help me!
Alex

Answer 1

Hi,
I guess one of the first things to do is check to see whether you're getting much competition on your WiFi frequency. AirRadar comes with a free 15-day trial, which should suffice for troubleshooting purposes. iStumbler is free, does the same job but I've never tried it.
You might also want to re-configure your wireless security just in case it's been hacked and someone is leeching off it. Unlikely, but worth checking.
Finally, your wireless speed is always limited to the speed of the lowest-speed receiver. So, if your iPhone 3GS is accessing the internet at the same time as your Mac you'll be limited to 802.11g speeds. So, double-check to make sure you haven't got a low-speed device connected, especially an 802.11b device.
That's all I can offer, I'm afraid. Good luck.
S.