Apache fails on start-up — what could cause this?

If the key file has a passphrase, you’ll need to remove it, as Apache cannot read this on start-up. You can do that with the following command:

openssl rsa -in file1.key -out file2.key 

file2.key will contain your unencrypted key.

If you downloaded the file via Mozilla, it may have saved the file in a compressed format.