Ever since I installed Parallels, the wifi on my Mac is intermittent -- even when Parallels is not running. The wifi will be up and running fine and then all of a sudden it wont be working. The only way to fix it immediately is to turn the airport off and then back on. If I do not do this, it will come back by itself after a several minutes (5 - 10). But even then I'll go down again at some random point. Right now I've resorted to always being plugged into Ethernet. How can I fix this?