Can't dial an external USR modem


I have an application using vaComm, vaModem and vaZModem that connects to various BBS and works fine on many computers.  One computer in particular has trouble.  It is using a USR external fax modem. it is an older modem, 2004.   It is using com port 1.  vaComm.Open works fine. := true works fine.  vaModem.dial executes, but nothing ever happens.   The modem doesn't dial and none of the external lights ever flash.  We've tried different com ports.   Eventually the vaDialTimeout event fires.
Are there any known issues with USR and/or external modems? 

I'm sorry but I'm not aware of issues with this specific type of modem.
From your description, it would appear that the modem doesn't receive data.
Did you verify you use a proper 5wire cable between PC & modem?

The modem was replaced with a modern USB attached USR Modem.  Now everything is working fine except for an intermittent problem with sending files.  Occassionally the VAZModemTransferEnd(Sender: TObject; ExitCode: Integer); event fires with exitcode = 0 even though the last bytecount from VaZModemFileProgress(Sender: TObject; ByteCount: Integer); is only about 60ish% of the entire file.     We can see the progress from procedure  VaZModemFileProgress go up as I compute the percentage inside the event.  It shows 5%, 10%, 15%... 60% and then suddenly the TransferEnd prematurely fires. The BBS on the receiving side is still in file transfer mode and  is expecting more zmodem packets.

It looks like I'm using v2.01 of the Async32 package.  is there anything newer?

It's unclear what version you use. The latest version is v1.4.5.0. See:

It's hard to tell what possible caused the premature interrupt. Did you test this first with a direct PC to PC connection?
The version property off the TVAComm component is  Is this the proper way to tell the version?
No we did not test it this way.  How would the PC's be connected?  What would be to gain from testing this way?

With this test you could exclude it is caused by noise on the line.