If you can't get the update to flash successfully try this method below.
I'm running the rooted stock 3.1, prefer not to have to restore to get this to work. Hoping to get a version that doesn't brick me.
The link above has the file.
I renamed dlpkgfile.zip to EP101_SDUPDATE.zip and moved it to root on microSD card. Power off eeepad then hold volume down & power button. Then press volume up when you see the text on the top left of the screen. It'll install the update. I'm now on 18.104.22.168. Cheers.