Could be a over heating problem - mine occasionally cuts out esp last week when the weather was extremely hot (so hot, that in 3-4 days it was declared a heat wave by UK standards only to be followed by thundering rain showers
).
Other thing could be too many connections open from a torrent client - if you got a bit torrent client running try limiting the number of connections it can have open - my older router used to extremely bad at this any time a torrent was downloading I would get internet drop outs.
Ali