We upgraded last night from 1.3.9h to 1.5.0, and now the admin navigation wraps on a 1024-wide screen. This is a problem because the "Admin Access Management" menu is now split between two lines (see screenshot above).
This means that if you mouse over "Admin Access," the menu shows up about 1em below the words, and if you move the mouse into the intervening blank space to get to the menu, the menu disappears as soon as the cursor enters the blank area. If you mouse over "Management" on the left side of the screen, the menu still appears about 1em below "Admin Access," and there's no way to get the mouse over the several inches of intervening space before the menu closes...
The screen is a little different on pages that don't have a scroll bar on the right, in that it is then the "Extras" item which is on the left, but it's menu is still anchored to the right edge of the screen.
I'm sure I can fix this with a certain amount of css modification, but it seems that at 1024px wide, what I expect is default navigation ought to work without modification. That leads me to believe this is a bug.