Sorry but with such slim details.

I can't guess if it's one of the known issue such as FIOS, or the router firewall or other.

But since you wrote it can't find the router, is the router within 20 feet and is the channel of the wifi one your Samsung supports?

Example at http://forums.cnet.com/7723-13973_102-560420/wifi-disconnects-from-time-to-time-galaxy-tab-7-plus/?tag=contentBody;threadListing

More at http://forums.cnet.com/7723-7589_102-378511/samsung-owners-start-here/?tag=contentBody;threadListing

Bob