Don't have the links handy, but the support forum threads show that none of the above is working in most cases. Some people are having limited success changing channels, but problem returning after a short while.
The key factor appears to be that booting into Windows on the same machine removes the issue - it's only happening in OS X, on iMacs (all other wireless devices working fine). Ergo, it must be something related to OS X software or OS X drivers.
It seems Apple are aware of the issue - just hoping for a fix soon, as I'm going to have a tough time explaining to my partner why the machine we just dropped £1000 can't hold a connection when the iBook G4 she's upgrading from could hold it fine.