Your MD's are using the same packages as the core/hybrid. My guess would be that your MD's have some sort of hardware issue, rather than software. The tarball used to create the diskless images for your MD's is based on the same image that is extracted during the DVD install for your core.
I would look elsewhere, in the logs, or using dmesg from a console while playing back media. Chances are something is improperly configured or there is a hardware issue.
Best of luck and Regards,