Once again the STA driver doesn't work for b43xx cards in Ubuntu 11.04. I know it's a kernel issue. I want to understand why it keeps getting broken? I can never upgrade with confidence that I'll have network connectivity when I finish. It worked fine in 10.04 and 10.10. Why can't you guys get this stable?
I'm sure this will be closed soon as argumentative or flame/trolling, but a better way to do your updates would be to test it out on live CD before installing. And as for kernel updates, that's why GRUB lets you choose old kernels in case the new one doesn't work properly for you.
Also the STA driver is closed source. The community has no control over it, it's up to Broadcom to fix it, so you'd be better of complaining to them.
Yes it is fixed or was yesterday when I installed it for my broadcom wifi
You may have to reinstall the sta driver
You could in a terminal try the following:
Not much more than that will be necessary
As the other answer says Ubuntu do not make the STA driver but Broadcom do. As kernels change so do the drivers at Broadcom.
There is an excellent guide for installing Broadcom wifi drivers here which will also help if you are off line as they give you a how to with no internet access if like me a few times you are stuck with no wired connection and you have broken the wifi: