WM_TIMER message handler in my program is called with significant delay - about 100-200 ms. Usually it's precision is 20-30 ms. For example, if I use
SetTimer(TIMER_ID, 1000, NULL); // in CWnd-deriver class
OnTimer function may be called with 1100-1200 ms intervals. What may be a reason for this? This program worked number of years without problems.