It could very well be a line noise problem, and there is nothing much you can do on your configuration. The log shows that it is negotiating, but failing during training. It then repeats the steps at a lower baud rate to compensate for line noise problems. Once it reaches 2400 bps without success (the lowest sending rate), it will disconnect and log as a failure in the WinFax logs.
One way to confirm if it is a line problem is to try using another fax modem (different fax model) and see if the results are the same, or using a regular fax machine (if you have one) from the same location to send a fax to the same recipient.