MBP: Wireless Connection extremely unstable

[majick]

Hi

I have a Macbook Pro 17 Inch High Res and my router is a D-Link DIR-635 1.09a Firmware.

For a few weeks now my wireless connection has been extremely unstable. Websites take about 10 seconds longer than they used to take; Downloads are very swingy and change from 5 Mbit/s to 500 Kbit/s within seconds. I am very sure my MBP is the problem since I tested a bit with various Windows-Machines and they would not have a single problem with the connection.

I am thinking it's either the airport-firmware that was recently updated as far as i know or 10.4.10 making trouble. Is there any way I can downgrade the airport-firmware to an older version? How can I do that? I've also tried changing everything router-related (ciphering, channels etc.), nothing worked.

Downgrading to 10.4.9. would be the very final thing for me because it's my understanding that I would have to backup all my stuff before downgrading, and I only just finished setting everything up… But if anything else fails then I'll have no other choice I guess.

Any advises?

 

[majick]

Update:
I called Apple Care today and they gave me some tips. I already did most of what they said except that I hadn't thought about making a new OSX-account to see if that would change anything. It actually did – WLAN was perfectly stable with the new account! So that means something is wrong with my system or the programs I got installed here. What could it be? Anybody have an idea what I should be looking for? Is there any way to "clean" the system…?

Any hint is appreciated!