problem related TCP/IP

Dear Team
I m very panic with this problem.Actually the problem is My PC is connected with LAN,overther different server based application are running Like SAP client,Lotus Notes,internet,Intranet etc.
I m not able to access any of the application.I m able to ping all the application Server.Also i m able to reach every where in my network but inspite of all this I m not able to access this application from clinet side.
I think It must be problem Of TCP/IP Suite.
which comes and go every times.but not able to trace why It is happening.Pls suggest