If it shuts down from a safe boot, that will generally mean some third party item is preventing a proper shutdown. Safe Boot disables those so that points the finger at one of them.
It you installed Snow over Leopard or Tiger or migrated everything over from a previous OS, there might be something incompatible. Or you may have installed some third party program since doing the Snow install.
This may help to find the culprit: fellow contributor etresoft has written a small program that may help identify what's interfering. Unzip it and run the app, then post the results here. You would run this booted normally.
Also, run this command in Terminal in Utilities and post the output. Just copy/paste it in and hit return.
kextstat | grep -v apple
It is possible, although unlikely, that the Safe Boot itself fixed the issue.
Message was edited by: WZZZ
Here are the results of the etresoft check.
iMac - model: iMac7,1
1 2 GHz Intel Core 2 Duo CPU: 2 cores
2 GB RAM
ATI,RadeonHD2400 - VRAM: 128 MB
Mac OS X 10.6.8 (10K549) - Uptime: up 0:0:25:5
WDC WD2500AAJS-40RYA0 disk0 : (232.89 GB)
(null) (disk0s1) <not mounted>: 200 MB
+ù+ (disk0s2) /: 232.57 GB (65.83 GB free)
Apple Inc. Built-in iSight
Apple Computer, Inc. IR Receiver
Apple Inc. Bluetooth USB Host Controller
Problem System Launch Daemons:
[not loaded] org.samba.winbindd.plist
Problem System Launch Agents:
User Launch Agents:
User Login Items:
3rd Party Preference Panes:
User Internet Plug-ins:
Top Processes by CPU:
Top Processes by Memory: