Is the UbuntuOne client broken for you on F18? Suffer no more! I've just updated all sources to the latest stable version, 4.1.2. But more importantly, I've included this tiny little patch which fixes this big bug related to libc 2.17. The RPMs are currently available at the fedora-ubuntuone-testing repo for a couple of days, and then will be moved to the "stable" fedora-ubuntuone repo.