It has been awhile since I've had to communicate directly with my modem, and
I seem to have forgotten whatever it was I knew....

Upon occaision, my modem ( Rockwell k56flex) fails to hang up.  It rings,
gets a busy signal and doesn't hang up.  However the dialer will attempt to
re-dial and receives a "no dialtone" response.  Meanwhile the line stays
open until the phone line begins making it's off hook complaint... which has
no effect on the modem.

Any suggestions?  i.e. is the darn thing showing signs of eventually
dropping dead, or is it a simple software thing?

Frank B Smith