Dock disappeared

Might be a good idea to trash the preference files for the dock and then do a kill -HUP on it. The files are located at:

~/Library/Preferences/com.apple.dock.plist
~/Library/Preferences/com.apple.dock.db

The ~/ denotes the home directory rather than the root just in case you were not aware.

It could be a "broken" JPEG in the Downloads folder, that makes the Dock crashing over and over again. I'd try to remove everything from the Downloads folder via command line.

Ahh was not aware that this would cause an issue. If so, killing the dock plist and db should also resolve it as it should clear everything off the dock (including the stacks I believe).

Would then need to troubleshoot individual stacks and icons on the dock by adding them one by one to see if problems occur, so removing the Downloads stack would probably be a quick fix to see if it works first.

I had this problem, and removing the "broken" jpg fixed it. Thanks for the advice!
If you have this problem, look for a broken jpg in your downloads folder before trashing the dock plist and db, just in case it fixes it - then you don't have to rebuild your dock icons and settings like I did.
This all assumes you have the default downloads folder shortcut in your dock like I do.

Yes, this solution worked for me too. After a download that included several image files, I started having the disappearing dock problem on an iMac 24" Aluminum running Leopard. At first it would appear and disappear quickly, repeatedly. Dock preference settings had no effect. Then, later, the Dock simply failed to appear at all.

After reading this hint, I connected to my computer from another and found a jpeg file in the Downloads folder. Moving it to the desktop fixed the problem. I had previously tried deleting the various dock prefs files and that didn't help.

Thanks for the solution!

Same issue, same solution!!
Began after downloading a jpeg in an email. Started working again as soon as I trashed that jpeg out of the downloads folder.
THANKS!

WORKED FOR ME TOO!

My Dock suddenly wouldn't appear, and spaces was freaking out. Preferences did nothing, reboots did nothing. I was starting to freak out.

I saw this solution and I was skeptical, since it seemed unlikely to fix the myriad odd problems I was experiencing. But, I just moved the JPEG from "Downloads" to my desktop and the dock sprang back to life, no reboot, nothing.

Thanks!

Worked for me too.
Astonishing that this should bring down part of the OS!

It worked for me as well... Thanks for the help! Just one broken jpg file and the whole OS was in verge of collapse!

There is another forum on this subject:

http://discussions.apple.com/thread.jspa?messageID=6424991#6424991

This was my post from there:

I appreciate the active forum on this subject, thank you all for the help. In the end, my solution to this problem is:

.) Command-Option-D did not work.

.) I tried the Terminal solution of:
killall Dock

.) Terminal solution did not work (other than reset my desktop background, which is kinda cool, because it was jacked)

.) After applying the terminal solution, and THEN using Command-Option-D my Dock came back.

Thank you for the tips everyone.

To summarize:

1) In Terminal:
killall Dock

2) Command-Option-D

Hope this helps,
Jon

PS: I have no image files or anything related during this most recent disappearing, that may be a separate issue. May the force be with you.

Great post... I had tried all the usual methods, reboot, trash prefs etc... pulling out all the files in my download folder took care of this issue...