I cannot place any file nor delete any file on my desktop. Other parts of the file system (like the Documents folder, Downloads folder, etc) seem fine. I checked permissiosn under the terminal and it's drwx for the user. I don't know what's wrong.
Besides traditional Unix user/group/others r/w/x permissions, file and folders in Mac OS X can be locked via Access Control Lists (ACLs, see
To see all those kinds of settings for your Desktop folder, do this in Terminal:
(I recommend you copy/paste that as the characters in it are hard to distinguish in some typefaces.)
If you're still stumped after seeing that output, update your Question with the output from that
You should run disk repair in Disk Utility in addition (and before-hand) to fixing permissions. And, ideally, you would do this after booting into another disk (like a recovery disk, or the disk that came with your system).
If this doesn't work, then I strongly recommend you boot into a DiskWarrior boot disk, and let DiskWarrior rebuild your disk's directory.