You should never call the MessageBox function from your FoxWeb scripts, because this will cause the message box to appear on the server -- not the client.  Obviously this will stop program execution, effectively disabling the channel until it is either killed by the FoxWeb Channel Monitor (if you have Restart Channels enabled), or until somebody acknowledges the dialog box on the server.

If you want a message dialog to appear on the client then you need to use JavaScript's alert method:

<script language="javascript">
alert('This is my message');
</script>

FoxWeb Support Team
support@foxweb.com