Internal Speakers not available in Audio Output

I have a 17 inch i7 Intel Chip 2010 MacBookPro running OS 10.8.5 that works correctly in all respects except that my Built-in Speakers stopped working. My Built-in Speakers worked perfectly until...

I was using Rosetta Stone software and it required plugging in (and using) the included USB mic/headset. The Rosetta software gave instructions to Open Preferences/Audio and choose the USB mic/headset as the input/output device (this muted the built-in speakers on my MacBookPro.

After completing the lesson, I unplugged the USB mic/headset and plugged in my external speakers into the Audio OUT port. Since I could hear the audio through the external speakers, I forgot to reset any settings in the Preference/Audio window.

When I disconnected the external speakers, and restarted my MacBookPro, I heard the Startup Chime (so I knew the speakers work) but, when I tried to listen to ANY audio through the Built-in speakers (from iTunes, video, clips from the internet, etc.) no audio was heard. Remembering I had to change back the audio settings, I opened Preferences/Audio/Output and the ONLY selection listed under Name/Type was Digital Out/Optical digital-out port. The Mute Box is unchecked and the Volume Curser is grayed out. There were NO OTHER options available so, Built-in Speakers was no longer an option. Without that option, I can't "choose" the Internal Speakers to turn them "on".

I have reset PRAM and SMC Power Management 4-5 times with no success. I have used Disk Utility to "VerifyRepair Permissions" (which was needed) and also checked "Verify Disk" (which didn't find anything wrong).

Does anyone have any suggestions on what to try next?