I'm trying to use a 123-reg generated certificate on a 3900 for management and SSLVPN. I've registered an A record for the public IP of the firewall:

vpn.companyname.co.uk - 123.123.123.123

then requested, valideated and downloaded the crt and pem file from 123-reg for the new certificate.
When i try to import by clicking upload in to the local Certificates section on the firewall and point it at the crt and pem files i get "error key file is invalid".
I've checked using notepad++ that it's in the Unix format rather than winodws/dos format.
anyone else managed to upload a public cert to a 3900 ?