The problem also occurs on an ATI Radeon 3000 with the latest available driver.
If you don't enable
GL_VERTEX_PROGRAM_TWO_SIDE, the problem does not occur.
A Visual C++ project to test the problem is attached. It has a Read Me with steps to reproduce, including the use of Application Verifier to make the problem happen reliably.
ShaderBugTest.zip 32.3 KB