Much discussion about this problem floating around.
It's an HTC Sense UI issue, where the widgets don't retain their settings and are lost upon a reboot or home restart.
Some widget devs are now adding a special "Sprint HTC Only" configuration as a workaround, but it has the negative effect of only being allowed to run a single instance of the widget. (though usually not a big deal.)
I've ditched Sense for Sweeterhome 2 and don't have this particular issue any longer. All widgets work just fine after reboots.