I had the same problem and stumbled upon this process. I don't know why, but it worked for me.
Connect your iPod and let it sync. Select (highlight) your iPod description on the left side of the screen under "devices", then select the "apps" tab (at the top of the main screen). This displays the available apps on the left side, and each of the simulated pages of apps on the right.
1) First, move the cursor over the white icon and click the black 'x'. This removes the white icon from the page. It also removes the check mark from the corresponding app in the list on the left.
2) Click the "apply" button in the lower right corner of the screen. iTunes warns you that this will remove the app from the iPod. Click "remove". The iPod will then go through the sync process. When it finishes, the app is removed.
3) Go to the available apps list on the left and check the box for the app you just removed. The app will appear (with the correct icon) in the simulated screen on the right.
4) Click the "apply" button in the lower right corner of the screen. This will re-install the app to the iPod. You'll notice that just before the sync completes, the icon will go white again.
5) Once again, roll the cursor over the white icon and click the black 'x'. This removes the white icon.
6) Click the "revert" button in the lower right corner of the screen. The correct icon will appear where the white icon used to be.
7) Click the "sync" in the lower right corner of the screen. When the sync is complete, the icons will be fixed.
I have had success performing this process on 1 white icon or many at the same time. Good luck!
