Could not establish secure channel for ssl/tls with authorit

We are facing a strange issue with our web based application developed in ASP.Net(C#) and hosted in IIS 7.5.

Our application communicates to few third party web services, each using SSL certificate. System works perfectly fine but some times following error occurs which stops all communication to web services.

Could not establish secure channel for ssl/tls with authority

When we restart IIS, this issue is resolved and system starts working normally. But after some times, issue comes again. We have tried all possible solution such as installing certificate, assigning certificate in code behind etc.

Thanks in advance