ok. ONE more time, so people can see that there is a fix, and this is NOT interference. I was doing perfectly fine with 10.5.2 with 7 strong signals around me, no interference. And when i updated to 10.5.4 it killed my connection. Everytime.
So! There is a fix to this, see the above posts. It works well.
his issue was quite different from yours (existing since tiger.) I don't think you two had the same problem.
His post describing that it has been fixed with an update sounds like the placebo is taking effect.