Intel 5100 AGN very slow Internet speed

[raku05]

hi,
I am having a strange problem. I have SL-300 with Intel 5100 AGN wlan card. Since 3 weeks, I'm having very strange problem, my internet speed has become very very slow (I've 20mbps ADSL connection), however, when I connect using wire, the speed is normal. Moreover, I've also Ubuntu Jaunty (9.04) installed on same machine and I've no problem with speed!!! I uninstalled and re-installed the driver but to no avail. My current driver version is 12.4.0.21, 3-4-2009.

I hope to get good suggestion.