[Cube] Power up problem

[John Derbyshire]

My replacement Cube from eBay (the original was stolen) has an odd 
power up problem:

it won't

unless it's:

1.  put it to sleep with the power up switch

2.  woken with the power up switch, then Cube begins to power up but 
never gets to the chime/monitor lights up phase but we can hear the HD 
whine

3.  after 10-15 minutes (never immediately) it can be booted with the 
reset button and powering up starts normally, everything fine after 
that.

Any ideas about what is causing this and what we can do about it would 
be met with a sustained round of applause!

thanks