Excel misteriously crashes when populatins a comboboxes

hi everybody!

When I initialize a form in my excel I run this code to populate some comboboxes:

Dim x As Integer
    
    CPIMenu.height = 545
    CPIMenu.width = 865

    CPIMenu.StartDate_Day.Clear
    For x = 1 To 31
        CPIMenu.StartDate_Day.AddItem x
    Next x

    CPIMenu.StartDate_Month.Clear
    For x = 1 To 12
        CPIMenu.StartDate_Month.AddItem x
    Next x

    CPIMenu.StartDate_Year.Clear
    For x = Year(Date) - 5 To Year(Date) + 15
        CPIMenu.StartDate_Year.AddItem x
    Next x
    
    CPIMenu.DesiredTripDuration.Clear
    For x = 1 To 90
        CPIMenu.DesiredTripDuration.AddItem x
    Next x

HERE THE EXCEL CRASHES ABRUPTLY! IF I ERASE THE .CLEAR STATMENT, IT CRASHES WHEN TRYING TO LOAD THE FIRST ITEM. I HAVE INVESTED QUITE A LOT OF TIME TO UNDERSTAND WHAT IS HAPPENING BUT IS IT IS A MISTERY. IF I UNLOCK MY VBA CODE WITH MY PASSWORD, THEN IT NEVER CRASHES... IF I CLOSE THE WORKBOOK AFTER UNLOCKING THE VBA CODE AND THEN OPEN AGAIN THE EXCEL FILE AND RUN THE FORM, IT DOES NOT CRASH. IT ONLY CRASHES WHEN I OPEN A NEW INSTANCE OF EXCEL, OPEN THE FILE, AND OPEN THE FORM.

CPIMenu.task1Day.Clear
    For x = 1 To 31
        CPIMenu.task1Day.AddItem x
    Next x

DOES ANYONE KONW ABOUT ANY BUG THAT MAY BE CAUSING THIS AND HOW I CAN SOLVE THIS MISTERY?!

THANKS IN ADVANCE FOR YOUR HELP!

FRED