I'm using the built in Harmony remote database for the Xbox 360 and the X,B,Y & A icon buttons will not work with my Harmony One remote in the activity mode.

I just checked the Xbox 360 buttons in device mode and they do work but they DO NOT work in the "Play Xbox 360" activity mode.

I've called Logitech and they didn't have any advice for me other than trying to learn those buttons in RAW mode but I don't have an Xbox 360 remote.

Any ideas?

Check if the Activity Customize Buttons uses the same command names (not the label names) as in the working command names in device mode.

I'm not sure if I read you right but I check the Xbox 360 in device mode from the Harmony software and the lists looked the exact same as the one in activity mode.

I'm going to delete the Play Xbox 360 activity and device altogether and then update it to see if it makes a difference.

What jlet meant was you may have 2 different sets of buttons that look similar but are different. "x" and "X" e.g. Look at the name of the command (NOT the label) and make sure the same command name (NOT label) that works in device mode is used in the activity buttons. If they're the same then delete and re-add the activity. Sometimes the activities get hosed.