X install with Matrox G450 locks system. A text install will complete but any attempt to run X after setup locks the system.
The G450 card is completely unsupported by XFree86 in Red Hat Linux 6.2. It is also unsupported in 7.0, and no stable support currently exists in my current XFree86-4.0.2 working tree. It will be supported at some point in time under a future version of Red Hat Linux, but definitely not for Red Hat Linux 6.2. Your only recourse is to obtain the latest 4.0.2 or later sources from XFree86 directly and build it yourself (with fingers crossed that the G450 will work - no promises), or to wait until a future release of Red Hat Linux that supports this card. I have a G450, so will be making every effort to integrate support when it is available. Again, not for 6.2 however.