[INTERNET] Telstra ADSL 2+ not performing as it should?

[Nik]

I've had this problem for about a year now. I was at a friends house, when I asked him what internet/plan he has. He told me the 50GB per month ADSL2+. He was getting 10mbps+ on his download and upload. I reccomended it to my mother, and within a month, we had it. It was performing as expected for about 2 hours, and then it went downhill. 240pp YouTube videos took ages to load, loading up a simple website was a problem, and we would have random dropouts.
Modem Model: technicolor TG797n v3
GB per month: 50GB
Plan: ADSL2+

Here's a picture of my download and upload speed:
http://www.speedtest.net/result/3209048761.png (Keep in mind that's the best results we've ever had)

Danke.