Logic Pro X Additional Content Download Freezes

OSX 10.10, Logic Pro X 10.1.1.

I'm trying to install additional content packages onto Logic Pro X. I keep running into one problem- the download works fine, and then freezes in the last five seconds of the download.

For example: I download 25 GB of plug-ins. The progress bar goes to 25GB out of 25GB and says '5 seconds remaining'. Then it sits there ad infinitum. I have waited about 6 hours for it to do something, but it's still sitting in the same place. Logic is not unresponsive, I can open a project and work on it, and all other apps work without a hitch.

I've tried with a large download (25GB), a reasonably sized download (14GB) and a small download (250MB) and exactly the same thing happens every time.

I can't use the app without this content.

Macbook Pro, i5, 4GB RAM.