I have recently upgrade to Ubuntu 10.04 a.k.a. Lucid Lynx, and have notice a significant drop in wireless speed. After dabbling about for a while and doing some google search, I have come to the answer 😛
Just run the command below and restart, and all should be well:
sudo apt-get install linux-backports-modules-wireless-lucid-generic
update [8th May 2010]: the latest update from Ubuntu has this by default. A quick update should solve the problem 😀
update[10th May 2010]: If you face problem with your wireless connection keeps dropping, and unable to connect back, please refer to my other blog post
BTW, if you have a CD/DVD in the CD/DVD drive, please remove it then restart. Else you might see the ksoftirqd/0 process hogging nearly 100% of your CPU.
Please refer to [ubuntu] Lucid Lynx Wireless Keep Dropping (updated) for more updates. I will be updating the post as i find out more solution on the issue.