Initial 2D panel size problem

Guys, my FSX SP2 runs @ 1152x864 resolution in full screen. My desktop is also @ 1152x864 resolution. Since recently all my aircraft panels started to load initially in 1024x768 resolution. I can't figure out, I recall I already saw it occasionally in FS2002, FS2004 but can't remember the remedy. It's annoying to drag the panel edges with the mouse to the screen resolution each time I want to fly. What did I mess up in FSX.cfg?Thanks.