iMac won't shut down or logout users

[film916]

I often have an issue where my iMac won't shut down, restart or logout users. Basically, when I click Shut Down or Restart, the desktop icons disappear as if the computer's getting ready to shut down (the desktop wallpaper remains) and it just sits there and won't shut down. I have to hold down the power button on the back of the computer in order to get the computer to shut off. This often happens when I try to logout a user. I'd say this happens about 2/3 to 3/4 of my attempts to shut down or logout a user. Any ideas?

[Hellhammer]

Reset SMC and PRAM and run Disk Utility

[richard.mac]

restart holding command+V and it will boot in verbose mode. then shutdown or logout and verbose mode will also show. what does it get stuck on?

[film916]

Originally Posted by Hellhammer

Reset SMC and PRAM and run Disk Utility

First, thanks for the replies, but you're kinda speaking a new language to me. How to I reset SMC and PRAM, and what should I run in Disk Utility?

Originally Posted by richthomas

restart holding command+V and it will boot in verbose mode. then shutdown or logout and verbose mode will also show. what does it get stuck on?

I don't think I've ever booted in verbose mode. What should I look for when I shutdown?

[richard.mac]

no need to reset the PRAM (actually NVRAM in Intel Macs) as it just holds the speaker volume, screen res and startup disk info. do try an SMC reset tho http://support.apple.com/kb/ht3964

if it shows verbose info before restarting, might not as you said it stalls at the wallpaper (not at the blue screen), it will stall at a line and try and remember what stalled it or write down the whole line.

[Hellhammer]

Originally Posted by film916

what should I run in Disk Utility?

Repair permissions and verify the disk.

[film916]

Originally Posted by richthomas

no need to reset the PRAM (actually NVRAM in Intel Macs) as it just holds the speaker volume, screen res and startup disk info. do try an SMC reset tho http://support.apple.com/kb/ht3964

if it shows verbose info before restarting, might not as you said it stalls at the wallpaper (not at the blue screen), it will stall at a line and try and remember what stalled it or write down the whole line.

Thanks, guys... I'll give this a shot and let you know what happens.