To work around this bug simply read the contents of the input buffer to clear it. Below is a reuseable routine that does this for you. Here is a command1 click event that will call the reusable routine to clear the buffer.

Private Sub Command1_Click()
    'Workaround for the InBufferCount bug
    InBufferClear Comm1
End Sub

Public Sub InBufferClear(CommControl)
    '================================
    'PURPOSE: Clear the Comm buffer
    ' (set InBufferCount = 0)
    'PARAMS: CommControl = A Comm
    ' Control Reference
    '===============================
    Dim Dummy
    Dummy = CommControl.Input
End Sub