I have a machine with Ubuntu 9.04 and a Broadcom BCM4306 wireless card which has been running quite happily for many months with the b43legacy driver that's suggested by Hardware Drivers. Suddenly, I'm now seeing crippling packet loss, varying between 30% and >90% when pinging the router. My WinXP machine is still quite happy even when sat next to the Ubuntu box, so I assume that it's not some new source of interference.
What else is likely to have changed? How should I go about diagnosing and fixing this?