Unable to redirect after cross domain authentication is done using SSO and Reverser proxy

Hi,
I have two applications namely ABHelper.com & ABViewer.com both are hosted in different server. I'm doing SSO between these (From ABHelpler to ABViewer) also using reverser proxy between these. Now my problem is once the SSO authentication is success on the second application, in few mins (or in any iteraction) my first app(ABHelper) is getting logged out. The requesting URL is as like "http://ABHelper.com/login.aspx?ReturnURL=/details.aspx"
Using cookies for SSO.
The Flow will be
ABHelper.Com/Login.aspx--(on success) ---->ABHelper.com/details.aspx---->ReverserProxy---->ABViewer.com/Login.aspx--(SSO)----->ABViewer.com/Home.aspx
I'm opening the ABViewer from ABHelper on clicking a link. After the ABViewer.com/Ho ...