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They could have set those up just in case people make typos when trying to reach the www. version. I would set up 301's from all of them to either the www. version or non-www version (check to see which is a better backlink profile).

Is this it http://www.seomoz.org/blog/new-guide-release-the-professionals-guide-to-advanced-search-operators Sean

Hi Rand and Anthony, Sorry about the belated reply; I haven't had any more problems over the last couple of weeks so as it stands, it looks all sorted. Thanks for the help!