I've read your thread, this to me sounds like there's water getting into the wires somewhere. I had a problem sounding just like yours for about 3-4 weeks in February. It drove me insane since I tried alternate routers, alternate ISPs, 4 techies all with Murphies Law syndrome. Line worked okayish while they were there, albeit all the packet loss that was going on... web pages could still load while gaming was impossible.
Long story short, I followed the cable along the wall of my house which eventually landed up in a manhole in my own driveway. I opened the manhole and low and behold there was a bunch of exposed wires sitting in the mud. Hint: one of those was my adsl line. It made sense to get the wire out of the water but I also had to cut, strip and re-wire it, then i protected it with about half a roll of insulation tape. At this point all I could think was screw waiting for yet another telkom techie. All those random intermittent drops, and packet loss issues vanished never to return. You need to trace you line as far as you can and check for exposed joints.
Otherwise I've heard alarm systems and electric fences can cause interference especially if the electric fence is arcing. If your adsl line is running next to other cables like alarm systems or microwaves this could cause the interference. Try and think if anything like that changed recently.
Good luck!