We recently got upgraded to two Sky+ boxes a few weeks ago. Before that we had one standard sky box and dish and our broadband worked no problem with this. When the sky engineer came to install the two Sky+ boxes in the house he used the existing setup to replace the sky box and installed a whole new setup for the second sky+ in a different room.
The engineer forgot to place a microfilter between the second installed sky+ box, the result, our broadband kept cutting out every 5-10 minutes and it was doing my head in.
We bought 2 microfilters off eBay for the all expensive price of £1.99 and I fitted one of them into the connection of the Sky+ box! No problems, our Sky and Internet work perfectly fine along-side each other, and we can even use the phone at the same time! Thats 3 things on one line! Nice!