Okay, it appears that this is a continuation of a bug in ASP 5.5.

Switch layers in 5.5 also cut off the pan/tilt channel, but it was the one layer type that did this. So it was easier to miss.

Group layers in 5.5 had that 'extra' space that Rasheed mentions below the last channel, so losing a scroll space didn't hide anything in 5.6.

As you can see here, bone layers in 5.5 had no extra space, so the addition of the order layers channel pushed the pan/tilt channel out of view.

Here is the 5.6 bone layer timeline, now missing the pan/tilt channel.

And finally, the original bug in 5.5 that only caused the pan/tilt channel of switch layers to be hidden, now causes both the roll and pan/tilt channels to be hidden in 5.6.
I hope this helps document the problem thoroughly enough that Mike will take note and look into fixing it. If it is not an easy fix, then I think a fair workaround fix would be to add maximize/restore functionality to the timeline panel.
This is REALLY annoying. I can't reach these channels unless I either remove some of the shown channels or cover my work area with the timeline window. I much prefer to keep all of the channels visible in the timeline, so I don't end up with keyframes I'm not aware of.
