extension wiring or filter which could be the cause. Seeing as you already replaced the filter, can you give a description of how many extensions you have please? Re: Speed up and down It happens 24/7 as far as I can see - I was downloading something which usually would take a few hours overnight the other night, and it wasn't even halfway done by the time I got up. It also happened all day during the weekend. I'll try switching everything off when I get home. Oddly though, whenever I've restarted my router it seems to restart the pattern - I always get the 7-odd minutes of good connectivity followed by the 25 minute slowdown. If it was external you'd presumably expect that I'd turn my router back on during the middle of at least one of the slowdowns. I'm in a quiet little village nice and near to my exchange - nothing heavy duty ever goes on here. Re: Speed up and down Okay, a bit more information. Turns out the problem only occurs when my main PC (connected via Ethernet) is on. When it's off, the internet performs normally. As soon as I turned on the main PC (and waited the requisite 7ish minutes), the problem came back. I'm going to boot to an Ubuntu live CD to try and determine whether the problem is with hard, firm, or software. I did mess around inside the computer the other day so I'll probably poke around in there