the firefox download is becoming a bit of a kneejerk reaction ...
a bit like using wireless, an iPod and an LG chocolate
if you want a different browser ... by all means download firefox ... if your connection is clearing ... it's possible that something else is afoot - whatever else explorer does ... this isn't one of the more usual things
if you are curious about FF ... download this version
http://portableapps.com/apps/internet/firefox_ portable
which won't impact on your system and try it ... it's useful for faults like this ... because it's not interfering with settings.
if you like .... then make the change - if not ... no damage done
before then
in explorer look in tools | internet options | general | browser history settings.
set the cache to between 500-800 and tick the "refresh everytime you visit" option
then look in connection
you don't say how you connect ... modem or router.
if its a modem ... check that the connection isn't set to cleardown after a set time.