Very odd verisign issue

rockstar81

Hello, I have been looking at an issue at work with a verisign certifcate we have. Basically when our iPads connect to the internal wireless network and browse to a interal web page that is signed with a verisign cert it rejects it (says it can't be verified etc) yet if I connect to the external wifi it will go to same site and accept it (web site is available internally and externally). Something is blocking the certifcate from being accepted - what I am trying to work out is what traffic/process does the device go through when it comes to a secure site and it is presented with a verisign cert?

Cert Poor

Is there an OCSP or CRL verification being blocked somehow internally? It may not necessarily use ports 80/443.