vidoe call problems

my folks and i have been using IM messenger with video for quite some time on
a daily basis with great service, but about 1 week a ago the video is
delayed, and the voices are scratchy and the words cut out all the time. We
have both checked our computers and our web cams to make sure they are in
working order and they are, so what can be the problem?

Please help us, as we are in the military and this is our line of
communication to our family while away for the ARMY.