I just learned that Firefox 31 contains a new Certificate Verification Library.
If you are running into certificate errors with Firefox 31 that were not happening before, it is important that you report them as soon as possible.
It's also important that you test your infrastructure as soon as possible.
More information about testing can be found in this Wiki article.
If you run into problems you can change the preference security.use_mozillapkix_verification to false and this will turn off the new verification.
This is not recommended, though, because the old code will be removed in Firefox 33, so we need to make sure we get any problems worked out.