Ive been fighting with a DIGI SP connected to a US Robotics Fax modem and the RealPort driver on a Windows 2003 server. I was able to get the modem installed and accessible to my fax software and successfully sent outbound faxes. However after a few days I checked back on it and noticed that I could no longer do so. When I access the properties of the modem in device viewer and click on "Query Modem" I was getting an immediate error and the event logs showed "Serial Port COM4 cannot be opened because it is open by another application."
I was able to resolve it by changing the COM port but I've already gone through this a few times.. Is there something else that I could be missing? It seems that after a few weeks the error returns.