Unable to import .ics files in Mavericks

Hey all!

Updated to Mavericks recently and I have been trying to update my calendar with an .ics file for a few days. I download the file from the website, and then when it is automatically opened by Calendar, I get "Calendar can’t read this calendar file. No events have been added to your calendar."

How do I fix this? I've tried downloading the file from multiple internet browsers (Safari, FF, Nightly), and nothing changes. I've also tried updating on my iPad as opposed to my MBP, and same.

Help please?