Hmmm, all posts are appearing with the text centered - but only with IE. FF and Chrome are displayed with the text left-justified, as expected. This is only happening with IE, and only on this site. Running IE without add-ons does not correct issue.
It is definitely a Windows7forums cookie problem. If I log out and delete my cookies then look at the posts, they are all properly aligned to the left. But as soon as I log in, the posts are center aligned again. And once again, only this site.
Thank you for identifying this problem. It was the result of a change required by Google in the placement of ads and the text surrounding said advertisements. It looks like we had a missed a </center> in some commenting out of code. bassfisher6522 also corroborated this problem and we were able to duplicate it in IE9 when advertisements are disabled. The problem has been fixed.