When you start glxgears you have this error X Error of failed request: GLXBadContext Major opcode of failed request: 143 (GLX) Minor opcode of failed request: 5 (X_GLXMakeCurrent) Serial number of failed request: 24 Current serial number in output stream: 24
*** This bug has been marked as a duplicate of 190245 ***
mesa-6.4.2-6.FC5.3 has been pushed for fc5, which should resolve this issue. If these problems are still present in this version, then please make note of it in this bug report.