Losing internet connection after 5 min of inactivity

I have a problem that's recently developed with my newest PC. (Lenovo, 64-bit). After 3 minites of online inactivity, my internet connection (FIOS), is lost. At this point, a "Work Offline" notice pops up. "No connection to the internet is currently avaliable. To view internet contents that has been saved to your computer, click work offline. Click Try Again to attempt connection. Try again does re-establish my internet connection. This situation started a few weeks back, and I've been using this PC for 4-5 months now. I'm not aware that I've changed any settings since initial start up.

I'm using FIOS's Actiontec router, non- wireless on this computer. However, my other PC is wireless and shares this same router. No problem with that computer.

I'm a hit and miss amateur with this computer stuff, ... and at the moment, unsucessful solving this problem. I know it's probably something simple, but I'm stuck. Appreciate the help.

Also, ..any opinions on using Carbonite as backup? My older Maxtor external hd, apparantly has a software problem with Vista, so I need to "homework" this issue. Thanks