If you happen to own an iPhone or iPod touch and you clicked at "Check for update" under "Devices" in iTunes, and you were told that "4.0.2 is the current version", there's an easy way out.
Download the official 4.1 IPSW file for your gadget - the right iPhone/iPod and the right generation (about 370 MB for iPod touch 3rd generation) - manually from this Uneasysilence.com page. Save it somewhere.
Once this is finished, go to iTunes and the only change is that you hold SHIFT when you press "Check for update". The SHIFT will guarantee that you will be asked to navigate to the IPSW file you just downloaded. Don't worry: iTunes will verify its integrity and version. In ten minutes in which you shouldn't disconnect your device, you're upgraded.
Don't stop reading... Well, you could actually have stopped reading in this case because you're finished. The comment doesn't always work. ;-)