ISA server problem

hi :
i have installed an ISA server 2000 which belongs to array in a domain …. the isa server works well but i can’t disconnect the connection manually .. i supposed that there is a worm on the server but i scaned the server with notron anti virus 2003 with the last update vision however the broblem still happen .. what is the supposed cause for this problem ?
another thing to ask : my clients try to bring thier hotmail e-mails through outlook express but the server is unable to bring e-mail ?!!!

thankx a lot