The AutomaticUpdater and wyUpdate work fine here (and with thousands upon thousands of other customers). Maybe you've encountered a bug. Or, more likely you've done something wrong.
I'm trying to help you debug this problem to see whether it's our bug or your bug.
So what should you do? This:
Look where your executable is sitting. Sitting next to it is wyUpdate.exe and client.wyc. When you run wyUpdate.exe next to where your executable is sitting, does it say you're already up-to-date?
Try replacing the ":wyUpdateLocation" property to an absolute path to where you know wyUpdate.exe is sitting.
Do I mean permanently hardcode the path to wyUpdate? Of course not. But you should do it when you're trying to solve this problem.