|Maybe the beer did more damage than you thought. You might have damaged the IDE or Sata (whichever applies, in your case) controllers on the Mobo. |
It may also be as simple as a cable needing reseating. If so, it'd be more than likely the IDE ribbon cables (or SATA cables if it applies) might have developed corrosion where they connect to the Mobo. Unplug and replug them a few times to wear away any dirt/corrosion.
The IDE ribbons and/or SATA cables are a part of the I/O pathways, to and from your optical drives.
Please let us know if you found someone's advice to be helpful.