REDEMPTION HANGING during LOGON

I have two applications developed in Visual Basic. Both the applications use REDEMPTION to communicate with EXCHANGE SERVER. The main application just hangs when the following command is executed, whereas the same command is executed perfectly fine with the second application.

Call oRDOSession.LogonExchangeMailbox(ExchangeId, ExchangeServer)

Can anyone suggest or help, to resolve the problem.

Thanks in advance for the help