There are a couple issues that I have read about that can cause this type of delay.
One issue that can cause video to lag audio, is if the Set top box is outputting video formats that the display has to format convert for display. The STB has no way of knowing how long the video delay was for processing. The workaround for this problem is to set your STB to always output the native format of your display & avoid conversions.
I'm not sure what Sony receiver you have, but another cause seems to be with receivers that don't have quality decoders or high processing power.
I'm certainly no expert on this topic, and I'm sure others will chime in soon with some more help.
