[PyQt] QtQuick can't compile shader program

[Evgeniy]

Hello.
I'm trying to port my application to python3+pyqt5.
PyQt5 is really needed for me because of QtMultimedia, that is absent in 
PyQt4.
So, I've built from sources and installed Qt 5.1.1 and PyQt 5.1.1.
But when I try to run my app, one of its windows, that is QQuickView, shows me 
just a grey screen instead of the content. And I see a lot of lines like this 
in console:
QOpenGLShaderProgram: could not create shader program
QOpenGLShader: could not create shader
QSGMaterialShader: Shader compilation failed:
""
QOpenGLShaderProgram::uniformLocation( qt_Matrix ): shader program is not 
linked
QOpenGLShaderProgram: could not create shader program
QOpenGLShader: could not create shader
QSGMaterialShader: Shader compilation failed:
""
QOpenGLShaderProgram::uniformLocation( matrix ): shader program is not linked
QOpenGLShaderProgram::uniformLocation( textureScale ): shader program is not 
linked
QOpenGLShaderProgram::uniformLocation( color ): shader program is not linked
QOpenGLShaderProgram::uniformLocation( alphaMin ): shader program is not 
linked
QOpenGLShaderProgram::uniformLocation( alphaMax ): shader program is not 
linked
QOpenGLShaderProgram::uniformLocation( fontScale ): shader program is not 
linked
QOpenGLShaderProgram::uniformLocation( vecDelta ): shader program is not 
linked

The same thing happens when I try to run any QtQuick _PyQt5_ example. _Qt5_ 
QtQuick examples work fine, so the problem is not in the Qt itself.

I run Ubuntu Linux 12.04 and I have Nvidia GeForce 8600 graphics card using 
nvidia-304 driver from repo. Qt is built with Desktop OpenGL support.

Any help would be appreciated.