You can try reinstalling WMP over itself, which may fix the problem. Assuming you're using WinXP.
To do this, shut down all instances of the player, including disabling it in the Taskbar (right-click the Taskbar > Toolbars > untick Windows Media Player in the list if present & ticked).
Next, navigate to C:\Program Files\Windows Media Player & double-click on the setup_wm file to reinstall it over itself.
Now check to see if the problem persists.
If not joy with that, you can also try the Windows File Checker click here (for XP) & click here (for Vista & W7).
If that doesn't resolve it either, you could try an alternative ripper like Exact Audio Copy click here. If this works, then you'll know your drive is not at fault. G