SBS 2003 and Exchange

[NovaSec]

Hi

Looking for some pointers with a problem and hope some body can shed some
light on this.

Got SBS 2003 running exchange server was working fine until i decieded to
connect PDAs to it, now our internal website works but OWA now will not
connect, if i type http://ourserver/exchange i get a 'there is a problem with
this websites security certificate' error which it has always done (i know
should have sorted it out) then if i click the continue to website, i get a
blank page which used to be our OWA login page.

I have read through and followed numerous microftsofts KB but cant find the
problem.

Thanks for reading and hopefully there is a cure before a the dreaded re
install.