Ive noticed with some types of modems that if it is set to com port 3 it would give me problems , some would give me trouble on com 1 aswell. I would first make sure it isnt sharing an irq , then maybe change the com port if it was still giving you trouble. Also , is your ISP V.92 compatable? There are certian features like, modem on hold , and others that can effect the modem in strange ways . I usually disable V.92 with a modem int string . GL 38
edit , make sure that the diamond modem isnt visible in any of the modem property pages , look in add and remove programs too for any leftover reminants