Error:20599 Cannot Open Sql Server

I had made a Exports Application in VB6,Sql Server7 & Crystal Reports 7 which was working fine but, I had to Format the Data Server for Virus reason & Configure Sql Server.

Configuration is perfectly done & Software is working fine but while accessing the reports on client machine i.e. on Setting action property to 1, it is giving an Error while opening Report file from VB.

Error:20599 Cannot Open Sql Server

I tried many things but nothing worked :( ...
Pls help, me out..