The click wheel is popping out?

Strange, I think your best way to find a solution would be to get in there and see if there is some crud blocking the wheel, or maybe a broken bracket. Follow this guide to remove the click wheel.

If you end up needing a replacement click wheel, we are currently out of stock but you can check back another day or try your luck on eBay.

Alex check this answer given by fun4us "it seems that there is some design flaw on the the new curved casing on the 4th gen. i've been reading thru different posts and this seems to be a recurring problem and needs to be addressed by apple. the board/clickwheel after a lot of use loosens up and creating some form of unstable contact, a solution i found is by adding a firm backing to it. i did this by inserting a piece of thin plastic (thin old credit card would do) between the board and the aluminum casing on the bottom end of the iPod. tried this with 2 of my iPods and it worked. of course you need to take the bottom plastic cover and the aluminum connector support with the 2 screws first" Why has my iPod click wheel stopped working? Since your click wheel still functions I assume that this is caused by the above described issues. Put a backing on it to support the clickwheel. Good luck and let us know if it works.