Lose all ability to access OWA and Blackberry access with new SSL certificate

Hi - We have a client that recently had their 3rd party certificate expire on their SBS2003 - Since that point we tried to generate a new one, but when we do install it in IIS we lose ability to access any services on it , so OWA doesnt work and neither do Blackberries pick up emails.

We have checked all authentication setupp based on this link:
https://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/A_1798-Exchange-2003-Activesync-Connection-Problems-FAQ.html

I also disabled forms based authentication in MS Exchange Manager as well but that didnt make a difference - i am not sure if its an error in the way the certiifcate is setup initially?

I previously had a nightmare with setting up a 3rd party one but cracked, though somehow the knowledge i learnt from that experience , i cannot apply properly in this instamce -
Are there any good sites that give decent step by step intructions on how to install an Internal Certificate?

Thanks