The games in Wales and Scotland during that RWC sold poorly in comparison to the French games, in particular Fiji vs. Canada at Millenium only drew appx. 45,000 to a 73,000+ venue as well Wales vs. Japan only drew 35,000 at the same stadium. Scotland vs. Romania at Murrayfield only brought in 31,000 to a 68,000 seat stadium. So these three games by themselves are responsible for about 103,000 of the unsold tickets.
Average Per Game Attendances at RWC's a very quick glance:
RWC 2007: 47,150
RWC 1999: 42,683
RWC 2003: 38,282
RWC 1995: 34,375
RWC 1991: 31,250
RWC 2011: 30,777
RWC 1987: 18,750