I've never noticed this problem with my external drives (identical Maxtor drives; I'll find their model number asap). Let's try to narrow things down a bit:
1) Have you tried accessing your desktop using a terminal? Perhaps try opening a terminal (Applications->Accessories->Terminal) and entering:
Code:
cd ~/Desktop # Change directory into your desktop
touch testfile # this will create an empty file, just to see if it causes your external to come out of standby
rm testfile # Removes the test file we just created
2) Try installing a different file manager such as Thunar. See if Thunar can access that folder on your desktop without having to wait for the external drive.
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