yes, i've tried deleting .mp3, .ipa, and .app files and they've all deleted.
for some reason the trashit app itself won't delete.
also, when my backup disk is plugged in, the backup files i deleted appear in the trash. I get the error code -8003 again when i try to delete them, and trashit won't work for those either.
That second link that i sent you has some terminal commands, that you can use. I don't know for sure, but I bet that you are gonna have to reformat that external.