If you have a Kindle 4 (that’s the one with the hardware controller and no keyboard), Amazon just released an software update .
I don’t have a Kindle 4, so I haven’t been able to test it out. There are no release notes, and the folks on Kindleboards  are saying it downloads very quickly, leading them to believe that it’s just a patch.
Have any of you downloaded and tried it out? Notice anything different?
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I just tried the update myself, and didn’t run into any trouble. Couple of things I should probably point out, though, especially for anyone who’s not really familiar with this sort of process:
 1. The file you’re going to download from the Amazon site is a zipped CPGZ file. That’s not actually the file you want to drag-and-drop into the Kindle drive icon on your desktop. (Don’t worry—you’ll know exactly what I’m talking about once you read the software update instructions, here .) Instead, double-click on the CPGZ file; the resulting BIN file is the one you’ll need to drop into your Kindle drive icon.
2. Also, if you’ve never before updated your Kindle, don’t freak out if it appears that the vast majority of your library has disappeared once the update completes. (Like, ahem, I just did.) Just give it a minute or so, and your library will rebuild.