Sql configuration for Deployment C# Win form application in multiple System

I have Deployed My Win Form application in 5 system But among them 3 system works properly but one gets slow at loading data and some time It tells Application not Responding,what i will do? I am using SQL Server 2005 which is located in a remote location. I have pinged,checked system resources where all system are same,network is fine,SQL is dynamic listening mode,Disabled the firewall and so on.