Heavy detail: Millenium vs 98 vs 95... And a coffee with this?

Ok... Here's something following my last post! ;) This is a tray icon/resolution detail I've noticed on my last project, and I want some advice: Download my sample project (it require msvbvm60.dll) and run it in 1024x768: The resolution 'll change for 800x600 and it'll display a fullscreen form with some message (upper left) and two command buttons (upper right)... click on the minimize one, resolution will change back to 1024... now double click (left button) on the tray icon, to show the form, again (Back to 800x600)... and try to click on any of the command buttons! Do you need to click once or twice to activate this command button? Really, try it! (Please tell me what it does by posting a reply...) The fact is that I've tried this program on 4 computers... The first, my comp, running Win 98, need two clicks (like if it don't get focus, even if I use SetWindowForeground...) The fact is if I use a popup menu (called with right click) to show it, everything is ok...! The second, a laptop also running on Win 98, need only one. The third, running 95, need two, and the last, running Windows Millenium, is ok and need one. What the hell is the difference...? Help me! (Don't forget to try this program in 1024x768 or any res different than 800x600)