Sporadic Internet Connectivity

Since the re-installation of Norton Internet Security, my internet constantly drops off.  Sometimes after 10 minutes, sometimes after 15, and so forth.  I get a yellow exclamation point on my internet icon in the tray and I need to disconnect and reconnect to my router in order to get internet connectivity again.  It's quite a nuisance and I would really appreciate any help i can get.  I'm running Windows 7 Home Premium 64-bit and Norton Internet Security Version 21.1.0.18.  I actually removed NIS from my laptop around 8 months ago and couldn't remember why.  After the re-installation, I remembered having the same problem then...