I use an HDTV for one of my computers' monitor. Usually it runs at 1920x1080.
About 60% of the time, the screen re-sizes to 1024x768 when I start ccleaner (2.16? Whatever the latest as of today is). Saw the same behavior under 2.15, so that's about 7 resizings over this week I've been running W7.
Nothing has been configured to differ from the default settings: I'm not running in compatibility mode, etc.
I haven't seen this with any other program. Seems pretty odd.
W7, ccleaner 2.15&2.16
Q6600, 4GB, Radeon 4850 -> Onkyo TXSR606 -> Vizio 1080p