General :: Program Crashes When Sending Email In Response To Click On Send Button

I am sending an email using SendObject. Sometimes it works, and sometimes it makes the computer freeze up with no error message. I have tried this with Outlook running or not running, seems to make no difference.

Code:

'The sub procedure below sends e-mail in response to a click on the Send button.
Private Sub SendMessagesButton_Click()

'For Access, define some object variables and make connections.
Dim myConnection As ADODB.Connection
Set myConnection = CurrentProject.Connection
Dim myRecordSet As New ADODB.Recordset
myRecordSet.ActiveConnection = myConnection

[Code] ....

I have added some MsgBox () to narrow down where it crashes. It is after 'Five' and Before 'Six'. On the line:

Set appOutlookRecip = .Recipients.Add(eMailAddress)

I am mystified as to why it works OK sometimes, and not others. The email address being used is valid.