I personally find that Keyframes are most easily managed in the Effect Control Panel, rather than work with the "rubberbands" for the Effects in the Timeline.
In the Effects Control Panel, one has control over the Fixed Effects, like Opacity, and any added Effects.
Does that not work for you? If you Select the Clip/Title, then go to Edit Effects, you should then be in the Effects Control Panel.
Bill, I just discovered the cause of the problem -- apparently a bug.
I neglected to mention that I had set some time-remapping at the end of the clip as well. If the time-mapping tool is engaged for a clip, then the key-frames changes do not work. I removed the time-mapping, and the key-frames changes started working as they should.
I tested this on both Windows and Mac. Both versions have the same defect.
One possible workflow, that comes to my mind, would be to do the Time Re-mapping, and the Keyframing separately. Say, apply the Keyframing, as needed, then Export/Share that Clip (can be limited by the WAB, Work Area Bar), then Import that resulting file back into the Project for the Time Re-mapping. One could also do the order of application of Effects in reverse too.
If one is doing an Export/Share to an intermediate file, for later editing, then this article might be useful: http://forums.adobe.com/message/4556586#4556586
Good luck, and thank you for sharing your findings - that was a new one to me.