Server Down after MySQL Search

[eluser]Unknown[/eluser]
Hi everyone, this is my first post here
I have an issue with a search page: after a search, generic search into a 2k records, some users have their IP blocked for some minutes to all server (I use netsons, the fast2 server).
This is probably caused by a very intensive activity to the server from that IP, so... how can I check that traffic? I've tried the debug log without errors so I don't know what it should be and my customers are quite upset...
Someone can help me?
Thanks