Request time out

Recently I set up a small office network which is having 10 computers with a “SuperCom EP-824DX” 24 ports swicth.I tested the network wires with a Lan Cabel Tester.All cabels ok.But the problem is when I ping after 2 or 3 replies there were a request time outs, then once a again replies. What could be the problem

thnx