uugetty under ISC 2.02

[Dave Veona]

I am having a problem with uugetty under ISC UNIX 2.02.  Once in a while
the transmit and receive lights on my modem glow continuously.  To quote
someone in this newsgroup, "the computer is having a shouting match with
the modem".  

What is going on here?  This happens when someone is calling in, not when I
dial out.  I have vanilla serial ports with no special drivers, but I do have
16550AN chips.  Modem is a Practical Peripherals 2400 with MNP.