I'm not sure exactly how/where this is set in Lion, but that shouldn't be too hard to figure. You might want to check what is set in the Finder's
Arrange by pull down menu found (so far) at the bottom of the
View>Show View Options window?
- If it's not
None, try that and see if the behavior changes.
- If it doesn't change, or if the menu's already set to
None, try changing it to something else and than back to
None, testing the Finder behavior after every change.
If that doesn't help or if this particular Finder setting cannot be found, please post back here and we'll try to come up with something else.