A different dialer wouldn't help you there, especially since you've narrowed
it down to being a lack of a remote response, meaning something timed out.
Look for the "loss of carrier" setting for your modem, and try doubling
it. There are other things too, but that's the most likely one IMO. There
are other timers too, for DTR, which you might try adjusting. If no help,
just keep track and put them back where they were.
Look for a pattern of some sort in the disconnects; time of day, period of
time online, whatever, if the above doesn't help. There are lots of things
can go wrong that can't be easily detected.
HTH
Pop`