ASP. NET application stopped responding.

Hi,
We have a working ASP.NET application(IIS7).
It worked till yesterday. This morning, it suddenly stopped responding.
It does not load the default page. Sometimes, login page loads. When it does load, it takes nearly a minute to load the page. It does not login. It does not throw any error but the browser shows that processing symbol.  Some times login will be successful but does not logout. 
I am not sure what is happening. We did restart teh server, recycled the application pools but nothing works. We have other applications installed on the same server all of which are working.
What might be causing this issue?

Thanks