Apple has initiated a repair extension program for the latest generation PowerMacs sold between October 2005 and August 2006 (including Dual 2GHz, Dual 2.3GHz and Quad 2.5GHz G5 models). According to Apple, if your PowerMac fails to start up after the power button has been pressed and its serial number falls within the given range (listed below), your computer may be eligible for repair free of charge.
CK539xxxxxx - CK608xxxxxx
G8539xxxxxx - G8608xxxxxx
YM539xxxxxx - YM608xxxxxx
RM539xxxxxx - RM608xxxxxx
More information about the program is available via Apple's support website.