Sounds like the Smartboard is running at an odd frequency (not 60hz) like an old CRT computer monitor. You can use the HDX's shutter and dial in the frequency and make the flicker go away.
1st, make sure you have Synchro Scan turned ON in the Menu section. Then, switch on the shutter at the front of the camera under the little cover, click around the settings to select SS and using the 2 buttons near the top side of the camera labeled Synchro Scan, you can fine adjust the shutter rate up or down to sync with the screen and remove the flicker.
Ernie Santella
Santella Productions Inc.
http://www.santellaproductions.com