Integration

Hi All,
I need ur hellp all in this please ,
Actually we have two servers
Database server &Application server
and there was working fine ,but for some networks problem our network guys change the IPs of the two servers
so now,
the database is running and I connect to it ,
the application server is not runing and i am getting the following error:
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No Response from Application Web Server
There was no response from the application web server for the page you requested.
Please notify the site's webmaster and try your request again later.
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I changed the url of the application server in the addess bar in internet explorer and still i am getting the same error ,i tried the put the ip in the address one time and the hostname also but it didn't work ...

in this case what should i do please help me guys ??

Thanks in advance ,

Ahmed