Hello... does anyone know why this made my vb6 not work? and i have to restart the computer in order for vb to work again?

Dim TimeNow As Long
Dim CurrentTime As Long

MSComm1.RTSEnable = True
TimeNow = GetTickCount
CurrentTime = TimeNow

' Busy wait here for 5 milliseconds
Do Until (CurrentTime - TimeNow > 5)
CurrentTime = GetTickCount
Loop

'Some code here

TimeNow = GetTickCount
CurrentTime = TimeNow

' Busy wait here for 15 milliseconds
Do Until (CurrentTime - TimeNow > 15)
CurrentTime = GetTickCount
Loop

MSComm1.RTSEnable = False

----- If i don't put in the 15ms busy wait and just go on.. then it will not crash... so I don't think it's the GetTickCount... any ideas would be greatly appreciated..
Thanx in advance! =)