Lost write privileges to external USB hard drive- please help!

Question

Hi,
I've got an external Western Digital 250GB USB hard drive that has been chugging along just fine until about a month ago, when somehow I seemed to have lost write privileges to the top level directory. I"m not sure if this happened when I installed an Mac OS update, or what, as I use the drive as backup and didn't notice it for a while.
The drive appears in the sidebar with a tiny lock icon, and when I try to copy a file from my internal HD to the external (top level directory, or drag the items right onto the icon), the following things happen:
Dialog box says "The item "foo" cannot be moved because "External HD" cannot be modified", with an authenticate button, which I then click.
After I authenticate, I get the error msg "The operation cannot be completed because you do not have sufficient privileges for some of the items."
But I *CAN** copy files directly into a folder that already exists on the external drive, but I cannot create new folders in the top level directory.
I have tried the following, to no avail:
1) "get info" on the external drive, checkign the permissions. In the Ownership and Permissions section, it says "You can Read & Write", and under details:
Owner: my account (dimmed) and access level is "read & write".
Group: my account (dimmed) Access: Read only
Others: No access
Ignore ownership on this volume (unchecked).
The fact that my account was named both as owner and group seemed odd, since in Group the access was "read only". I clicked on the little lock icon next to Owner, authenticated, and was allowed to change the Group settings. I changed the Group access to "read & Write", but it's not "sticking" -- when I close teh details field and reopen it, or close the get info window and reopen, the Group access settings go back to "read only".
2) I've also, of course, tried repairing permissions on my internal startup drive, which did not help the matter. Also in Disk Utility, I verified/repaired the offendin external USB drive (no problems), Verify/Repair permissions were dimmed for this drive (I assume becuase it doesn't have MacOS X installed on it?)
3) Searched the forums, Western Digital support, etc. and I cannot seem to figure out what has gone wrong.
4) When I connect the drive to another computer (my iBook) the situation is the same. Also, when I create a new admin user account and try to access the drive from that account, I still cannot write to the drive.
Thanks, I appreciate any tips or pointers.

Answer 1

The drive appears in the sidebar with a tiny lock icon, and when I try to copy a file from my internal HD to the external (top level directory, or drag the items right onto the icon), the following things happen:
Open the Terminal in the /Applications/Utilities/ folder and enter the following:
chflags nouchg
followed by a space; next, drag the disk into the Terminal window and press Enter. The lock should now be gone.
The fact that my account was named both as owner and group seemed odd, since in Group the access was "read only".
Recent versions of Mac OS X create a group with the same name whenever you create an account from the Setup Assistant or System Preferences. The Group permissions don't apply in this case.
I changed the Group access to "read & Write", but it's not "sticking" -- when I close teh details field and reopen it, or close the get info window and reopen, the Group access settings go back to "read only".
Did you get an error message after doing this?
Verify/Repair permissions were dimmed for this drive (I assume becuase it doesn't have MacOS X installed on it?)
That is correct. The Repair Permissions mechanism uses data from the /Library/Receipts/ folder on a disk to function, and this data is only present on disks which have Mac OS X installed.
(12377)