I’ve got a ThinkPad T61 with Intel iwl3945 wireless chipset that I installed fresh with Ubuntu 8.04. Everything worked flawlessly out-of-the-box, except for the useless fingerprint scanner and the wireless LED. Don’t get me wrong, the wireless network worked fine, but the LED wasn’t on.
At first I thought there was something wrong with the LED itself, but a couple of searches later I found that it was a known limitation of the 2.6.24 kernel included in 8.04. A driver upgrade was scheduled for 8.04.1 and after a couple of months it was shipped. Silly me thought I’d get the upgrade automatically, but it turns out that both the iwl3945 and the iwl4965, as well as a bunch of other wireless drivers, are tucked away in linux-backports-modules-hardy, which will not be installed by default.
So, if you have some wireless issues in Ubuntu 8.04, try installing this (meta) package (that depends on a suitable version specific kernel) and see if it helps.