1) That doesn't sound normal. Is the source in question a DVI or HDMI source, or does it happen with any source? When this happens, do you still get audio after the input change? Can you power cycle the TV or source ahd also re-gain the picture?

2) There has been some talk about this among 990 users who also use the 7500 or 7700 amp (including myself, as I have a 7500). When the incoming signal format changes, the combination of 990 and 7500/7700 seems to produce a low "click" noise. This is normal, although I haven't heard a technical explanation for why it occurs when it was not present with my old Model 750 amp or my M200's.