I figured it out....
If you go into an audio clip's properties and set the offset field to something other than zero it creates the situation described above (where at the end of the clip appears a grey vertical line with triangle at bottom).
Still not sure what this is supposed to mean other than a visual indicator that the offset for that clip is not 0....
Also, not sure if this behavior exists in later versions of Sonar or the latest CW, but just thought I'd follow up with the answer.
Sonic