won't sleep

Hi, I'm using a new MacPro, 10.5.7. I had Energy Saver configured to sleep from 11p - 5a every night, and was under the impression that it was doing so. The slider is on "never" so it does not sleep during the day in case I have to remotely access it. I had to pull up the system log the other day and noticed that activity was taking place during these hours. So I observed at 11p last night and the machine did not sleep as scheduled. I did not even get the dialog box with the countdown confirming that it is about to go to sleep. I have my 2007 iMac configured with the exact same settings and it sleeps no problem. Any suggestions on where to start looking for the problem?
Thanks

the Pro sleeps when you close the lid and i would assume this is what is causing the differences in your settings. you can also set the Pro to "Wake for network access" in your energy settings.

I do have the wake for access box checked. Sorry, not sure what you mean by close the lid. It's a macpro desktop, not macbook pro.

oops my bad i was thinking i was in the notebook section sorry about that

don't know if this helps but I manually put it to sleep last night and not too long later it woke up on its own. The entry from the system log:

Jul 16 22:08:17 MacPro kernel[0]: System Sleep
Jul 16 22:08:19 MacPro kernel[0]: Wake reason = PCI
Jul 16 22:08:19 MacPro kernel[0]: System Wake

Anyone know that this may mean?

is this something that would solve your issue?

hmm good question. my guess would probably concern your settings. try sleep when not in use in like certain hours? but if that does not work, please tell me!