Conexant HCF V90 Data Fax RTAD USB Modem

Since installing WindowsXP Service Pack 1 i can no longer
connect to my ISP on a regular basis. It takes
approximately 20 to 50 dialups before I can dial in. If I
am running Microsoft Media this reduces to about 10 dial
ups before a connection, I have no idea why this should be
but this is the case. The modem works perfectly well on
another machine running Windows ME. One of the messages
that I get in the log file is DSR low cannot initialise
the modem.

Can anyone please help