Can't connect to Symantec LUA from Chrome

Hi, 

I have a problem to connect to the LUA from Chrome or Firefox, I'm getting the following error (Chrome)

ERR_SSL_WEAK_SERVER_EPHEMERAL_DH_KEY

I know that it is happening because the server is trying to set up a secure connection but, due to a disastrous misconfiguration, the connection wouldn't be secure at all.

The question is: How do i fix it? How do I change the SSL/TLS Diffie-Hellman Modulus to 2048 Bits?

Thanks in advance