Got the 550 and set up the activities; watching TV, watching DVD, listening to Music, etc. The problem I have - and others must have had, too - is that when you select an activity my TVs power gets toggled no matter what the state.

In other words, I am watching TV, but now I want to "Watch DVD". The TV should be left on, the input changed, AMP and DVD player turned on. But the power toggle command is sent to the TV and turns off the TV. Conversely, when switching back to "watch TV" I want to switch inputs on the TV, and turn off the receiver and DVD player.

Is there a way to set up an activity so that doesn't happen?

Yes - there are ways. You have a few different options. All are done in the Harmony Remote application. Basically, go back into the setup for the each activity, and there should be some options as to what to do when leaving activities. In that area you have an option to leave certain devices turned on.

There are also ways to tell the Harmony not to turn your devices on or off at all, but that is a somewhat blunt maneuver.

There are other threads in this forum on the topic, likely with more detailed explanations too, if you wish to search a bit.

Good Luck!

You have the TV power commands set up as discretes (separate buttons for on and off) but you're using a power toggle. Find out whether the power commands are discretes or a toggle (try all of the commands in device mode that look like on/off or power commands - there may be several). Then setup the TV's power accordingly. If it knew your TV was a power toggle it would not be resending the command when you switch activities.