Concerning the sudden price moves, I just stumbled upon an article - it's in German, but contains some interesting charts:
http://www.goldseiten.de/bilder/upload/gs20111201-201420.gif
Source: http://www.goldseiten.de/content/diverses/artikel.php?storyid=18056&seite=0
http://www.goldseiten.de/bilder/upload/gs20111201-201426.gif
Source: http://www.goldseiten.de/content/diverses/artikel.php?storyid=18056&seite=0
These are average intraday charts, which are created by taking the average of intraday charts over a longer period of time. Although they have to be taken with a huge grain of salt (they are normalized to 1000, so even the largest spikes are less than 0.1%) the author points out that the spikes that occur just before the fixings might indicate that someone tries to keep the price low (yeah, I know... this price manipulation story again

but the charts look quite interesting anyhow...)
However, something like this does not explain the
upward spikes, as they happened again today just
before the fixing... :/ ?!