Directory index forbidden by rule:/var/www/html/

To be precise lemme tell you what behaviour am i facing.I have
developed an ASP.NET application using C# and i want to run it on RHL
9.0/Apache2.0 using mod_mono Mono 1.0.I have installed everything
successfully(i guess so) from Daniel's notes step by step.Now if i run
the same application under windows/IIS it runs PERFECT absolutely but
when i run it under RHL 9.0/Apache 2.0/mod_mono/Mono 1.0, i get the
weird behaviour.It run fine for some time...but after some time it
seems that the connection to the server is lost if the application is
left idle(probably 30 minutes).It starts giving the SERVER ERROR HTTP
500 for this particular application.If i try accessing the other
directory under root i.e /mrtg that also works fine but the problem is
with this particular application only which use C# with mono run
time.In order to fix that problem i need to restart the linux box and
everything starts running perfectly.I dont know what the problem lies
in and how to fix that up. I am using Session variables. I haven't
checked the cookie settings on my Windows and redhat box, but I'd like
to know and change any setting that can run my web app without
crashing. Any help or useful links will be of great help.I have
checked out the error_log file and it says that [client 10.6.10.19]
Directory index forbidden by rule: /var/www/html/. If i reboot the
linux box now it will start working perfectly without changing any
permissions at all . btw the permission to the directory where i have
placed my app is 777 and its chowned by apache and groupd is also
apache.
All the help will be highly appreciated.Somebody please help...to
figure out this behaviour