I have the same machine, and a similar problem, I hit the spacebar and it wakes, but quickly goes right back to sleep. This happens 2 or 3 times, then it seems to stay awake. No restart required. I, like you, have seen several mentions, but no real fix.
A > Periodically, I lose the keyboard and mouse "after" hitting the > spacebar to wake from sleep. It has all the appearance of a Finder > freeze. Obviously I have prior USB connectivity, or the spacebar wake- > up wouldn't work. Either connectivity is being dropped or it is a > Finder freeze. The monitor is up, no keyboard and mouse, and the only > way out is a hard shutdown and reboot. It has occurred individually > on all of my Applications, and several times right at the Login > panel. Began in 10.2 right through 10.4.5. > > On my iBook with the same devices connected?excepting external > keyboard and mouse, same Applications running, consistently on the > same update version as the G5, it has never happened to date. It > would lead one to believe it to be a G5 DP problem :) > > I have done all the usual alternate key combinations, disconnecting > devices, alternate USB ports, quitting Applications, trashing plist, > resetting Energy preferences etc., but the problem persist?twice this > week! I have a new commercial grade protector, have checked line > voltage, checked plugs, and have a dedicated 40 AMP breaker with no > other loads on the circuit, so I believe the power problems to be > eliminated. > > I have searched Apple Support, and various search word combinations > in Google. I find lots of reference to the problem, but nothing > definitive as to the solution. Anyone heard or read of a solution? > TIA...jf > | The next meeting of the Louisville Computer Society will | be March 28 at Pitt Academy, 6010 Preston Highway. | The LCS Web page is <http://www.kymac.org>. | List posting address: <mailto:macgroup at erdos.math.louisville.edu> | List Web page: <http://erdos.math.louisville.edu/macgroup>
