Okay. Got rid of the wrapper div. Took the float that had been in the wrapper css and moved it to the blogtitle. Took the clear:both from the blogtitle and moved it to the menubar. Got rid of the spacer. Everything works now, though I had to get rid of the 1px white border around the blogtitle in order to do this. (The 10px red top border had been contained in the wrapper; to move that to the blogtitle, I had to get rid of the 1px white top border that had been there, and so I got rid of the 1px white top border in the menubar, too.)
More info than anyone but me needs, but I want to remember what I did….