What the Hell Happened?

Last night I was listening to my system. As happens occasionally, the top end was shelved down from normal. Some high freq. air was missing, music was a little closed in sounding. Like I said, this has happened every few days for about 2-3 months. I've always thought it was either unidentifiable audio gremlins or my hearing was a little congested that night(I am 51 yrs old now). However, when I picked up the CD case for Someday My Prince Will Come, Miles Davis, my finger touched the metal top of the CD transport and there was a slight "snap" sound and immediately the music opened up! I could easily hear it while standing in front of my equipment stand! I sat down and listened to the last two CDs I'd played and all the high end extension and air was back, and it stayed the rest of the night!! Anyone have any idea what happened and how I can prevent it or correct it when happening again?
Thanks to everyone for the responses. I will try everything (I've turned up the humidifier on our furnace, gets cold here in Michigan.). I am using an outboard DAC and will try resetting when/if it happens again. I also have noticed that music sounds better, more personal and involving later at night. I think it has to do with the power being fed to my system, and the fact that I'm getting much less "inter-sensory" interference and can (on an almost subconsious level) relax much easier. No lights anywhere, hardly any sounds, etc. Thanks again for all the creative thinking.
Tom, I experience the same ONLY in my left ear a few minutes now and again, having just turned 50. A form of tinitus, I suspect?

A few years ago a doctor told me to wear the foam type earplugs (I use Howard Leight brand Super Leight - orange in color) each night when going to bed. I was starting to notice some tinitus (slight ringing) in my ears. His theory is that our ears need complete relaxation at times and earplugs give that during sleep. Since starting this practice I swear my tinitus has reduced somewhat. It certainly has not gotten worse.