Mine was doing that a lot too (icon dissapearing, losing connection)...
I changed the verizon FIOS router from B/G to G only, same difference.
For grins (and $49), I bought an N router and disabled the wireless on the fios router. Hasn't dropped once since (5 days)... Still testing...
Not saying N is faster, I can't tell, but the range seems a little better and the drops have stopped. Fingers crossed !