The way mIRC closes down was changed in v7.15 to resolve this issue. A number of shutdown routines, including the unloading of DLLs, are now called immediately when mIRC detects that it is being closed. Previously there was a small delay for some shutdown routines that may have resulted in them not being called during a WM_ENDSESSION event. The order of shutdown calls is still the same as v6.35 and v7.14 however. Can you track down the cause of this issue to a specific call in your code?