I am beginning to wonder whether there are some issues with Steam at the moment. I have noticed several thread popping up with people claiming to be experiencing very slow download speed and having downloads stop on them for no obvious reason. Example 1 Example 2 and Example 3. I too am receiving many of the issues that people are complaining about and despite some people in the threads listed trying the age old ‘ClientRegistry.blog’ deleting trick they are still getting the problems.

Valve seem to know that something is up judging by this post.

The fact that downloads sometimes stop/pause is a bug. We are working on identifying the cause and hope to fix it soon.

I will try and keep my eyes on this issue, I hope it gets resolved soon, I am sure Valve will sort this out, time will tell though.