It is hard to tell you the problem, based on 3/4 lines of very basic info.
There's 101 reasons as to why your internet's connection is failing.
Some basic tip's for you to try and see if you get any improvement.
- Make sure that all cables are connected properly. (Fully inserted)
- As you say that it's suddenly began to fail, contact your ISP (virgin, BT) and explain the problem to ensure you have no fault's
-Turn off your computer unplug the modem at the mains (and the power lead) after 30/40 second's plug both back in, turn on PC and see if there is any diffrence.
If the basic steps above fail, then your contact your ISP (BT, Virgin media) and explain what the problem is, and they should be able to sort things out.
I personally had my broadband upgraded about 2 week's ago and when the engineer left, there was no connection to the internet, so I unplugged the modem (as mentioned) and re-started my pc and it worked fine after that.
This is just some basic info which I am hoping you find sort's your problem out. If not, I have sent you my personal email address which you are welcome to contact me and explain in more depth the problem and I will try and resolve the issue for you.