After installing Ubuntu 11.04 on my Dell D620, I began noticing some wireless connectivity issues. This included delays or problems connecting to my home wireless network, increased latencies particularly when transferring files, and occasional disconnects. After upgrading to Ubuntu 11.10, the problems got worse. Doing some searching online revealed some possible solutions.
Installing the “b43-fwcutter” and “firmware-b43-installer” packages and rebooting the laptop is what ultimately worked for me.
aptitude install --quiet --assume-yes b43-fwcutter firmware-b43-installer