Not just always the exchange distants, like in my case, it is the line outside thatw as hid by lighting. The error at my pc is like 50 per minute. 50m to the box on the corner the errors is none. Now I can only have a 384kb/s line.
On the farm, I'm 5.5km from the exchange and I can have a 4mb line.
Bad wiring can also be an issue. Any idea what the Telkom wiring within your house is like? If there's a problem with the internal wiring, it will also affect your connection. I know because Telkom was out to fix one of my two lines (a non-ADSL one), and while he was working, he messed up my DSL line (noise margin decreased and attenuation increased). I noticed this as I was monitoring my figures (knowing that he could mess up my DSL line inadvertantly). I pointed it out to him and he carefully looked at the wiring again and fixed up what he had done.
Perhaps you can ask Telkom to look into the wiring?
What are your noise margin (signal to noise) and attenuation figures? Are you synching at 2048Kbps?
I allways thought that the wireing and the fiber will only affect you when you have ADSL2+ I mean If people are not getting full speeds on a 4mb line then what speed will they get when 8mb lines come out or even 24mb ADSL2+? Hmmm