There seems to be many problems relating to this, and no one has a solution..
However, here goes. I've got a mini9 running winxp. For whatever reason it no longer wakes from standby - after working for years. Perhaps this started after being in sleep for over a week and completely draining the battery.
When I close the lid, or when idle long enough, the screen goes black (as it should) however the power light no longer flashes. I've got hold the power button down and restart to the computer to get it out this state. Very annoying. The only solution that works is to disable standby in the power options (from control panel), including when closing the lid.
I twiddled with the 'USB wake from Sleep' (BIOS) and the hibernate option from the via the command prompts 'powercfg' program. No luck.
Seems to be some sort of flaw with these otherwise desirable netbooks.