This is late in the day (2 years) but for anyone trawling the web looking for a solution for an Archos 7 or an Archos 48IT that records out of sync using the DVR, read on.
For both units, make sure the output is not configured to HDMI. For Archos 7 use the pin reset hole to shut down and then insert on DVR, it will boot up on the DVR, go straight to DVR recorder and it will record in sync. If you play or do anything in the interim it will probably lose sync. Note I have been doing this for over a year and the pin reset is now very difficult to use but it works. The 48IT is easier. Full reset on unit then mount the unit on the DVR, press the power off button and select power off option, then press reboot option. Leave on DVR and it will boot up on DVR. select later on TV display and then go straight to record. It can do several recordings without losing sync but to be safe reboot between each recording. This unit can get very hot and produce corrupt indexes as a result so I have a fan blowing on it when recording long things in warm weather. Other glitch I notice is when warm both units can record when warm in a way that causes some AVI players such as VLC to freeze for a split second. I have found keeping recorder cool to be solution for this particularly if I am doing a marathon record (10 or 12 episodes of a series in one session).