Why does this script:

-- Begin Script
set theItem to {alias "Macintosh HD:Users:chip:Pictures:dog_cats.jpg"}
tell application "Finder"
        set comment of item theItem to "Test Test"
end tell
-- End Script

Yield this error:
        "Finder got this error: A descriptor type mismatch occurred."

I receive the same error if I tried to set a variable to the "comment
of item theItem".

-- Chip