If that doesn't help, the next thing to try would likely be asking for support from the linux wireless community: http://linuxwireless.org/en/users/Support. We don't really have enough expertise to figure out where an issue may lie without detailed info like a kernel OOPS statement.
@Jono:
Please try the upstream mainline kernel to see if it's any better. Packages can be found at: http:// kernel. ubuntu. com/~kernel- ppa/mainline/. Please try the latest 2.6.33 kernel.
If that doesn't help, the next thing to try would likely be asking for support from the linux wireless community: http:// linuxwireless. org/en/ users/Support. We don't really have enough expertise to figure out where an issue may lie without detailed info like a kernel OOPS statement.