I found out that a update to libcairo2 version 1.11.3+git20111109.90b2fd34-0ubuntu0ricotz lead to this problem. Downgrading back to version libcairo2_1.11.3+git20111015.3813066f-0ubuntu1~11.10~ricotz0 the gtk+ apps got rendered right on the screen.
Also, if I disable the oxygen-gtk theme or start the application with another theme the problem goes away. The problem occurs in natty too and the attached file shows four screens, on the right side the bug shows up.
Disabling desktop effects does not solve this issue and this also affects my laptop with intel video and xorg from xedgers.
From now I had to stick to the version of libcairo to the one that works good, its a temporary fix I think.
ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: xorg 1:7.6+7ubuntu7
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Fri Nov 11 08:59:51 2011
InstallationMedia: Kubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
ProcEnviron:
LANGUAGE=pt_BR:pt:en
LANG=pt_BR.UTF-8
SHELL=/bin/bash
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
Sorry for do no attempt to this at bug reporting, but I should had named it with [xorg-edgers] as this version of libcairo2 comes from this ppa.