If you have a Conexant(Rockwell)SoftK56 PCI Modem, this generic driver works.
This is a little bit of a hassel but I have speeds between 50,667 & 53,000bps now. This will update the windows comm driver to 6/08/00 but you'll need to immediately turn around and delete all the new driver files it installed except the wdmmdmld.vxd and reinstall your original files (unless your running W2k or NT, I'm running ME). The new AT will change to SoftK56V_B2.1_V2.07.02. It works for me and my driver search is over.