I just recorded a lengthy bass line via piece meal (i.e. one section or clip at a time).  After completing it, I played the song back to find out a couple of the clips were grayed out and muted.  All of the track lanes for the bass track are unmuted.  While experimenting, I right clicked on one of those grayed out clips and saw an option "Clip Mute/Unmute".  I clicked on it and it un-grayed (or unmuted) one clip.  This option seems to no affect on the other clip.  It remains grayed out and muted. 

I've checked my X2 Power manual (of course, that's for X2 and I'm using X3) but have not been able to find anything to address this issue (which includes doing a search on this forum.)  I've also tried unmuting the clip using various methods but the clip remains grayed out and muted.  It should be noted the graying out appears kinda weird, too.  The clip is gray and the sound waves are just the outline of the soundwave with no color in them.  I thought they should be more silhouette-like in appearance.  So, I'm not sure what's going on here.

Sounds like you've both muted the clip (the graying), and muted a region of it (the dotted waveform outline). Hit K on the keyboard or click the clip once with the mute tool to unmute it, then sweep the muted region in the top of the clip with the mute tool to unmute the region.
 
 

Wow!!  Thanks a lot brundlefly.  I was able to unmute that region.  That's a huge relief.  I don't know what I did to cause it to mute in the first place but if it happens again, I've got a new weapon on my duty belt.  Thanks!!

There's a hot key for muting. If you had all tracks selected and hit that key (K) you might have done this.
 
http://www.cakewalk.com/Documentation/default.aspx?Doc=SONAR%20X3&Lang=EN&Req=Menus1.181.html
 
 
 

I am using Sonar Platinum steam edition (version after Sonar X3) and I found I could move the track if I exposed the sub lanes and move that