modem issues

[Adam Myrow]

I'm just guessing, but slow and non-response might mean an IRQ conflict.
Since you said it is on ttyS3, type "dmesg | less" to look through the
kernel messages right at bootup.  See if it picked up the port and
assigned it the right IRQ.  There is a Modem howto which has a lot of good
information.  It may be installed with Linux already, or check for it at
http://www.linuxdoc.org.  Lastly, were you using wvdialconf to try and
detect the modem?