I ran into a problem with some certs some time ago and wanted to write about it for future reference. It was due to some certificate issues and it's formatting or something of the likes.
While the openssl command line utility had no problems with them, network manager refused them to be valid certs.
What was needed to be done was to remake them with openssl
$ openssl pkcs12 -in original.p12 -out temp.pem
$ openssl pkcs12 -in temp.pem -export -name "Repackaged PKCS#12 file" -out new.p12
All this was taken out from a bug report on launchpad.