OK, I don't know if this is the source of your problem, but there is an ACL (Access Control List) set for Desktop where I don't think there should be one. (That's the + near the end.) And the group, where it should be staff, is showing yourusername "dianarivera" instead (the group is the second listing of "dianarivera.") There may be a few other issues in other items in your Home Folder.
We could try resetting the Permissions and changing the group by using a small easy to use App "BatChmod." But perhaps it may be worth trying to just globally reset the Home Directory Permissions and ACLs to restore to the Leopard defaults to see if this fixes this issue. Not sure of this, but I think the migration and Archive & Install from Tiger may have been the problem. But first, now that you are more comfortable using Terminal, you need to run several commands in Terminal. Here are the directions from that article.
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To remove ACLs, open the "Terminal" application (located in the "Utilities" folder) and enter the following command:
sudo chmod -RN ~
Then users should run the following command to ensure the files in the home folder have them as the owner by running this command:
sudo chown -R `id -un` ~
NOTE: these commands should be run when users are logged into the affected account.
After supplying a password and allowing these commands to run, users should boot off the Leopard DVD, and after selecting a language, choose "Reset Password" and select the boot drive. Then select the user account that's affected and click the "Reset" button in the "Reset Home Directory Permissions and ACLs" section. After this has run, quit the installer and restart the system.
http://reviews.cnet.com/8301-13727_7-10329971-263.html
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So, open up Terminal and copy and paste (as typos can be disastrous with sudo, don't try typing it in.)
sudo chmod -RN ~
As I said before, you will get a standard warning about using sudo and you will be asked to enter your password, which you won't see echoed on the screen. Then hit enter and wait until you get a new $ sign prompt. Then copy and paste and hit enter.
sudo chown -R `id -un` ~
If you run this second command within five minutes, you will not be asked to enter your password again. Then wait for the new $ sign prompt and type in "exit" and close the window. That's it for Terminal. Then onto the Reset booted from the Install disc from the directions above.
When finished, see how the Desktop is behaving and then run the ls -l command again to see what things look like there now. You boot off the Leopard disc by holding down the c key at startup.
Also, I don't see anything untoward happening by doing this, but it would be a good idea to have a full backup, either a clone or Time Machine, to restore from just in case. (It's
always a good idea to have a full backup.)