Using firebug live-edit I altered the bits you mentioned to this:
.singular #content, .left-sidebar.singular #content {
margin: 0 0;
position: relative;
width: auto;
}
.one-column #content {
margin: 0 0;
width: auto;
}
and it seemed to do the trick. Thanks very much for the help!
This might seem like a silly question (still learning…!) but how did you isolate those particular parts of the CSS code? I’ve been using firebug but can’t seem to get that specific like you did.