Unusual Pc Cases Something Very Unusual Network Problem?

Something very unusual network problem? - unusual pc cases

Hello everyone, is a very rare problem that we face in our network of 30 PCs. We have 30 machines in our society between the 2 Mbit / s connection. The network configuration is in two years. Everything works fine, but in the last four months is very rare, these local Netwrok hangged in every 20-30 minutes, and if that happens after every reboot of the modem. If this happens at a time, a thousand millions of PC packages are sent when the checkpoint TCP / IP. See photo: http://img13.imageshack.us/img13/7077/networkproblem.jpg

He is someone who can help in this case. Thanks in advance