I don't think this is a ubiquity bug because I don't see it in Ubuntu, but testing Lubuntu i386 20120421 the ability to resize a partition shows you can increase the size but a broken icon indicates that you can't decrease the size. But if you click on the broken icon you can still decrease the size of the partition so it's purely an artwork thing. Could this be due to recent python changes?
I'm including a screenshot.
DistroRelease: Ubuntu 12.04
Package: lubuntu-artwork 0.27
ProcVersionSignature: Ubuntu 3.2.0-23.36-generic 3.2.14
Uname: Linux 3.2.0-23-generic i686
Date: Sat Apr 21 10:45:33 2012
LiveMediaBuild: Lubuntu 12.04 "Precise Pangolin" - Beta i386 (20120421)
PATH=(custom, no user)
UpgradeStatus: No upgrade log present (probably fresh install)