Yeah, I had that with my last ISP. I was with TalkTalk and was having trouble with my line. For some reason, my download speed dropped by almost half, and it kept disconnecting. They sent a third party engineer out (not BT engineer) who refused to check my line and told me to open my routers firmware in Internet Explorer. I sat down at my computer and proceeded to open Chrome and quickly logged into the router. As soon as I had logged in, he had noticed that I wasn't running Windows and commented on it. He even said that it wasn't a iMac. I told him that it was Linux. So he said that what needs to be done may not work on Linux. So he proceeded to change a couple of settings on the router to govern how it connects to TalkTalk servers, not to my computer, which was and is currently connected to through LAN cable.
The changes in router settings rectified the disconnection problem, but not the download speed. He charged me £60 for him not doing his job and left. After several months of fighting tech support, even though I was running Windows Vista at the time, they were saying that Linux is causing the slowdown, and the problem wasn't their end. I them went on the forums at http://www.moneysavingexpert.com/
and asked for help, and complaining about TalkTalk.
To my surprise, TalkTalk has at least one representative who frequents the forums and noticed that I was dissatisfied with them. After a few posts and private emails, it was brought to my attention that as soon as TalkTalk had brought out a new server side technology (software or hardware, I don't know) called Dynamic Line Management, it halved my speed to increase stability. He had the DLM turned off on my account, and my download speed went back to almost what it was.
I'm now with a new ISP with higher download speeds, and better stability.
However, TalkTalk doesn't support Linux, even though their servers are run on Linux.
Next time I have to get complain to LoveFilm, I'll mention that they do support Linux, because their systems are running on Linux.