Ethernet Keeps Randomly Disconnecting

It's plugged in via an Ethernet Cable from a Homeplug Adapter, since the modem is not in the same room as me. Basically, I've been having problems with the internet randomly disconnecting and for no reasons. There's some days where it'll go fine, no problems at all, other than a few things that always disconnects it, then there is days like today, where it keeps connecting every time I try to go to a webpage. I cannot seem to upload anything to the web (Youtube, Mediafire, etc.) without the internet disconnecting before it uploads. The only other problem that I've had constantly, even if it is working fine, is I cannot seem to do a video call on Skype or really use my webcam to broadcast online without my internet disconnecting. Also, when I play games via Steam such as TF2, Call Of Duty, etc., I have no problem with the internet at all, it works smoothly and never crashes when I play games. And the desktop is the only thing that ever has this problem. We have 1 other desktop, and 3 laptops (all connected wirelessly) and they do not disconnect from the internet at all. This has been going on for quite a while, and I'm still not certain on what is triggering it.