Re: V5.0 to V5.1 problem
I'd add quote marks around "center" though I'm not sure if that'll help. I'm wondering why the break tag is displaying. You could delete it; clearly it isn't doing what it was meant to; I wonder if this is related to the content display problem.
About the other question, on the Look and Feel admin page, under the General layout options (tiki-admin.php?page=look#content2), about half way down the page, left and right column can be given a "Only if module" option for displaying.
-- Gary