Have you looked to see if there is still a standby light on the board indicating it has power? I don't remember off the top of my head if the CHVF has one but that would confirm or disprove a power issue.
A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station…
I registered to hopefully save you from all the trouble that I went through setting up WOL.
A few questions:
Are you by chance using a Linksys router with stock firmware?
Are you trying to do it on your local network or over the internet?
Have you assigned your computer a static IP both on the client and Router (DHCP)?
If you are using a Linksys router ( just making a shot in the dark here) and trying to do WOL over the internet with stock firmware, it won't work (from what I can tell). Cisco doesn't like for you to forward broadcast, especially on the home user level. You would need something like dd-wrt (has great WOL support) to accomplish this.
From the sound of things, your router is clearing its ARP table and not keeping a record of the assigned IP address (which is why it works for a short period). If you were to make a static entry in your DHCP table for the computer that you wanted wake I believe that would alleviate the problem (locally).
You can set up your WOL program to broadcast locally, but it would require a subnet other than /24 (something like 255.255.255.128). I'm assuming Linksys here again.
This is my understanding of it and from the sound of it you're facing the same problem I was. It is most likely a router issue. I hope this helps and I would be more than happy to try and help further.