hey i'm having the same problem using Mandigo 1.41 but only in IE not Firefox. It happens when I use IMG to to display photos which are wider than the post column. Mandigo automatically resizes images to be displayed to the column width, but even if I change the width in the IMG tag the column still appears wide.
if you open http://bubikes.bostonbiker.org in Firefox it works.
but it only happens in IE8.
Strangely enough, this site is running on MU and the site admin also left a very old version of Mandigo (1.71 release in 2006 vs 1.41 released this past May) and if I switch back to 1.71 everything shows up in IE8 just fine.