Having just updated my browser to Chrome 19.0.1084.46 (the current stable version), I can now reproduce exactly the behavior you describe.
When viewing my profile with expanded information, everything looks fine. But when I click "less info" from that view, the layout breaks:
If I then refresh the page, leaving it set to display "less info", the top info header no longer overlaps the tabs below it, but the right-hand column is still incorrectly sized. The header box no longer extends across the entire width of the page.
Same deal on Meta Stack Overflow, Super User, and Server Fault. Not broken on the "grainy" theme used with the SE 2.0 beta sites.
Not a huge bug, but worth a few minutes' investigation.