When drag&drop element in window, the screen is blinking

[Arnold_Layne]

When drag&drop element in window, the screen is blinking, it looks like restart window manager. Video nVidia GeForce4 MX 440 AGP 8x, driver nouveau (nv18).
Running xcompmgr with no keys, periodically stdout drops:
error 9 request 148 minor 4 serial 3157
error 4 request 54 minor 0 serial 3224
error 8 request 151 minor 6 serial 3841
error 9 request 148 minor 4 serial 3842
error 4 request 54 minor 0 serial 3901
error 160 request 148 minor 7 serial 3902
error 8 request 151 minor 6 serial 20760
error 9 request 148 minor 4 serial 20761
error 4 request 54 minor 0 serial 20831
error 9 request 152 minor 1 serial 24830
error 3 request 20 minor 0 serial 24831

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: xcompmgr 1.1.5-1
ProcVersionSignature: Ubuntu 3.0.0-15.24-generic 3.0.13
Uname: Linux 3.0.0-15-generic i686
ApportVersion: 1.23-0ubuntu4
Architecture: i386
Date: Sun Jan 1 19:32:15 2012
InstallationMedia: Lubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
SourcePackage: xcompmgr
UpgradeStatus: No upgrade log present (probably fresh install)