Session Timeout problem when ASP.NET application is accessed remotely

Question

 I have a ASP.NET application, when I access this application from the local computer it runs fine. But When I try to access this application remotely i.e someother machine then there is a session time out problem every now and then. This doesnt happens with all cases. But many times it happens. If any body came across this type of issue let me know.

Sesison is ired before session timeout in rempotely.

this is happens in one page only. because it takes time to refresh the page i'e is (5 min).
no other page doesn't take  this much time.

iIset session timeout is 20 min in web.config.
and in IIS also 20 min.

what shoud i need to do tosolve the problem.

please help me out.
it's very urjent

thanks in advnce.

jaya