Audio/video sync issue free revolution

Hello, everything is in the title, for about a month I have been experiencing a sound and image delay that can reach 3 seconds. Despite the reboots and calls to Free, I am on the verge of canceling my contract. I have been with them for a year, and with the old Free, I did not have any problems. The responses from the hotline staff are really ridiculous, like "Oh, I see you have an iPhone and a laptop connected via Wi-Fi; that's where the problem comes from." Oh, but of course, I'm so stupid for not thinking to unplug everything or to turn off my laptop. Anyway, there is a case opened with them to look into the problem, which apparently is well-known on their end given some posts I’ve seen online. What outrages me is that I paid over 100 euros to change this Freebox, so with the delay, the Blu-ray player (big crap) that doesn’t read my DVDs, I am really fed up, and let’s not mention these incompetent hotline staff. There’s even a delay when I connect my external hard drive. I would like to know if you have had the same problem; here is my setup: TV box via HDMI on LED Regza TV.

Configuration: Windows Vista / Internet Explorer 8.0