iMac with OSX 10.5.5. I have a strange problem that i can't figure out what is causing it....I'm a bit of a Mac novice. Sometimes when i reboot my Mac, like after an update, the computer will reboot and will only load up my wallpaper and mouse pointer and will hang there until i hard reset it by holding down the power button. It doesn't even get to the point of asking for login credentials. After the hard reset, it will boot just fine. Does anyone know where i should start to look for a solution to this problem? Are there any maintenance tasks that i should be running similar do a disk defrag on a PC? Any help will be greatly appreciated.