Frontend server OWA loading hang

I update my backend server win2003 sp1 but i did not update the frontend
server,after that
OWA in premier client did not working just page loading until 10 minute
nothing happened.
If using basic client it's working but you cannot reply ,compose new message
and add
attachment ,just read only.
But if using OWA(backend server)for internal no problem at all,just the
frontend server(dmzzone) problem for exteranal OWA access.