A network-related or instance-specific error occured while establishing a connection to SQL server !!!!

Hello everyone,
 
I am working on a project using VS2010 SQL2008 and I saw an ODD behaviour ,
First let me tell you that the app runs without any problem in my developing pc (Windows Xp sp3 32bit)
 
But when I was trying the application in another pc (Windows 7 32bit)
 
I got this exception:
 

A network-related or instance-specific error occured while establishing a connection to SQL server.The server was not found or was not accessible.Verfiy that the instance name is correct and that SQl server is configured to allow remote connections.

 
Now what is weird in this exception; Is when the application reaches the DataAdpater.Fill(dataset) line I got this exception but when
the app reaches the DataAdpter.Insert(....) It runs without any problem .
 
And what is more weird is that I noticed that the dataset that is used in the previous insert procedure can later be filled with dataAdapter.Fill(...) procedure which it was giving me an exception .
 

Now I hope you understand my problem
 
I tried these things as a solution:
 
1)Checked SQlBrowser running..
2)No aliases to Sql server at all to remove...
3)remote area connection--OK
4)TCP and UDP port 1433,1434 exception in firewall
5)Unistalled my only antivirus Norton
6)Added Tcp/IP ports in Sql protocols
7)My connection String is : onnectionString="Data Source=ALI\SQLEXPRESS;Initial Catalog=PALMSDATABASE;Integrated Security=True"
8)Also tried using Sql Server authentication (user Id and password)
 

My question is what is the difference between fill and insert?
Is there a problem with my connection?
My app. runs smoothly on the original pc ,What should I do?
Please If anyone knows anything help me, I am very desperate.