Disabled sleep, but mac pro still sleeps!

Question

I've got a Xeon Quad Core Mac Pro, running 10.5 Server (10.5.5 to be specific)
This computer provides services for a small office network, and I've disabled sleep, but it still goes to sleep sometimes. I went into System Preferences --> Energy Saver and disabled sleep. Below you can see in system.log when the computer went to sleep this morning. How do I definitively disable sleep?
I wish I knew what "Previous Sleep Cause: 5" meant, so at least I could know what triggered the event.
Thanks for any leads.
If this is the wrong forum, please advise where would be more appropriate.
--Peter
Here's the output of pmset:
sh% pmset -g
Active Profiles:
AC Power -1*
Currently in use:
sleep 0
displaysleep 5
autorestart 1
hibernatefile /var/vm/sleepimage
hibernatemode 0
powerbutton 0
womp 1
disksleep 0
ttyskeepawake 1
system.log
Jan 15 10:54:18 hostname watchdogtimerd[44]: Automatic reboot timer disabled for sleep.
Jan 15 10:54:18 hostname kernel[0]: AFPSleepWakeHandler: going to sleep
Jan 15 10:54:20 hostname kernel[0]: Intel8254x -- Link Down -- 00:1f:5b:3a:5d:38 -- called by disable() --
Jan 15 10:54:20 hostname configd[29]: AppleTalk shutdown
Jan 15 10:54:20 hostname kernel[0]: -- Auto-Negotiation Advertisement Register (04d) = 0xde1
Jan 15 10:54:20 hostname kernel[0]: -- Auto-Negotiation Link Partner Ability Register (05d) = 0xcde1
Jan 15 10:54:20 hostname kernel[0]: -- Auto-Negotiation Gigabit Advertisement Register (09d) = 0xe00
Jan 15 10:54:20 hostname kernel[0]: -- Auto-Negotiation Gigabit Link Partner Ability Register (10d) = 0x3800
Jan 15 10:54:20 hostname kernel[0]: -- PHY Specific Status Register (17d) = 0xaf08
Jan 15 10:54:20 hostname kernel[0]: Intel8254x -- Link Down -- 00:1f:5b:3a:5d:39 -- called by disable() --
Jan 15 10:54:20 hostname kernel[0]: -- Auto-Negotiation Advertisement Register (04d) = 0xde1
Jan 15 10:54:20 hostname kernel[0]: -- Auto-Negotiation Link Partner Ability Register (05d) = 0x0
Jan 15 10:54:20 hostname kernel[0]: -- Auto-Negotiation Gigabit Advertisement Register (09d) = 0xe00
Jan 15 10:54:20 hostname kernel[0]: -- Auto-Negotiation Gigabit Link Partner Ability Register (10d) = 0x0
Jan 15 10:54:20 hostname kernel[0]: -- PHY Specific Status Register (17d) = 0x8000
Jan 15 10:54:21 hostname kernel[0]: System Sleep
Jan 15 11:11:45 hostname kernel[0]: System Wake
Jan 15 11:11:45 hostname kernel[0]: Previous Sleep Cause: 5
Jan 15 11:11:45 hostname kernel[0]: USB caused wake event (EHCI)
Jan 15 11:11:48 hostname kernel[0]: Intel8254x -- Link Up -- 00:1f:5b:3a:5d:38 -- called by interruptOccurred() --
Jan 15 11:11:48 hostname kernel[0]: -- Auto-Negotiation Advertisement Register (04d) = 0xde1
Jan 15 11:11:48 hostname kernel[0]: -- Auto-Negotiation Link Partner Ability Register (05d) = 0xcde1
Jan 15 11:11:48 hostname kernel[0]: -- Auto-Negotiation Gigabit Advertisement Register (09d) = 0xe00
Jan 15 11:11:48 hostname kernel[0]: -- Auto-Negotiation Gigabit Link Partner Ability Register (10d) = 0x7800
Jan 15 11:11:48 hostname kernel[0]: -- PHY Specific Status Register (17d) = 0xaf08
Jan 15 11:11:48 hostname kernel[0]: Intel8254X -- Negotiated Speed: 1 Gb/s, Duplex: Full, Flow Control: Receive Pause Enabled,
Transmit Pause Enabled
Jan 15 11:11:50 hostname kernel[0]: Intel8254x -- Link Down -- 00:1f:5b:3a:5d:39 -- called by enableHardware() --
Jan 15 11:11:50 hostname kernel[0]: -- Auto-Negotiation Advertisement Register (04d) = 0xde1
Jan 15 11:11:50 hostname kernel[0]: -- Auto-Negotiation Link Partner Ability Register (05d) = 0x0
Jan 15 11:11:50 hostname kernel[0]: -- Auto-Negotiation Gigabit Advertisement Register (09d) = 0xe00
Jan 15 11:11:50 hostname kernel[0]: -- Auto-Negotiation Gigabit Link Partner Ability Register (10d) = 0x4000
Jan 15 11:11:50 hostname kernel[0]: -- PHY Specific Status Register (17d) = 0x8040
Jan 15 11:11:50 hostname kernel[0]: AFPSleepWakeHandler: waking up
Jan 15 11:11:50 hostname watchdogtimerd[44]: Automatic reboot timer re-enabled.
Jan 15 11:11:48 hostname /System/Library/Frameworks/ApplicationServices.framework/Frameworks/ATS.framewo rk/Support/ATSServer[2
34]: ATSFindFolder timeout. (domain:-32763, dirType:'font', createFolder:false, ATSServer pid:234)
Jan 15 11:11:51 hostname configd[29]: AppleTalk shutdown complete
Jan 15 11:11:51 hostname configd[29]: AppleTalk startup
Jan 15 11:11:51 hostname com.apple.KerberosAutoConfig[13606]: Kerberos configuration is up to date
Jan 15 11:11:52 hostname com.apple.KerberosAutoConfig[13611]: Kerberos configuration is up to date
Jan 15 11:11:53 hostname mDNSResponder[31]: Note: Frequent transitions for interface en0 (FE80:0000:0000:0000:021F:5BFF:FE3A:5
D38); network traffic reduction measures in effect
Jan 15 11:11:56 hostname configd[29]: AppleTalk startup complete
Jan 15 11:11:57 hostname com.apple.KerberosAutoConfig[13648]: Kerberos configuration is up to date

Answer 1

I found this at macosxhints:
#define kIOPMClamshellSleepKey "Clamshell Sleep"
#define kIOPMPowerButtonSleepKey "Power Button Sleep"
#define kIOPMSoftwareSleepKey "Software Sleep"
#define kIOPMOSSwitchHibernationKey "OS Switch Sleep"
#define kIOPMIdleSleepKey "Idle Sleep"
#define kIOPMLowPowerSleepKey "Low Power Sleep"
#define kIOPMThermalEmergencySleepKey "Thermal Emergency Sleep"
not sure which one would be cause 5 - but interesting that there is a tag for Low Power Sleep as well as Thermal Emergency Sleep - perhaps you need to monitor the temperature of the machine and or the quality of the power on the line.