Don't assume the problem is with your computer.
If your ISP is having technical difficulties reaching YouTube, or is deliberately throttling traffic to YouTube, there is nothing you can do at your end other than to call them up and complain. Of course they will probably blame your computer instead of admitting their problem -- and most people will have no way to check because they only have one ISP.
However my brother is currently paying for two ISP connections.
AT&T U-Verse will break off 1.5GB downloads from GOG.com at around 250MB. However U-Verse seems to handle YouTube videos without issue.
Our Earthlink Cable connection is able to download the full 1.5GB downloads from GOG. However YouTube videos suffer frequent pauses for "caching" that sometimes never recover until the browser is closed and cleared.
So the same computer, same operating system and configuration, same everything except the ISP used --> different results. Try playing YouTube with Earthlink, and it halts. Switch the ISP settings to connect through U-Verse, it works and I can play YouTube videos for hours. Switch back to Earthlink, the halts and frequent pauses are back. Same can happen with downloading from GOG, only with GOG it's Earthlink that works better.