I have quite a stack of A105 boards showing this symptom, so for me it is worthwhile to find out what's causing it and how to fix it. If anyone can offer any insight, I would appreciate it. I have a known good adapter, jack dongle, and power button board. From there, the power does indeed enter the board past the socket. The fuses appear to be functional.
On one motherboard, there is a tick...tick...tick sound with still no other activity. I noticed that most of these A105 boards have very very poor solder joints, solder balls, pools of flux, solder peaks sticking up, etc. I didn't see any obviously crossed or dry solder joints, but I suspect that's a large amount of the reason behind all these board failures.
My email address is email@example.com and my website is winchesterpc.com. You can also AIM or Yahoo IM me at benvanderjagt