Nautilus has a specific function, which name I don't know, but the behavior is:
Typing a symbol from the keyboard opens a small box on the lower right part of the window and selects the first relevant file or folder in the current folder in the window
typing more symbols selects the relevant file or folder or no selection if the searched string doesn't exist in the current folder.
The backspace key deletes the last symbol used and again selects the appropriate file or folder.
Now this was in Ubuntu natty 11.04, in Oneiric 11.10 the behavior is like in the following:
Typing a symbol selects relevant file/folder, i.e. same as in natty.
typing more symbols... - the same as in natty
Backspace opens the upper directory in the tree and the small search box in lower right corner stays with the last searched string.
Typing anything from the keyboard adds more to that string even in the new folder and the only way to search from the beginning is to select the string /with the mouse/ and delete it with del button /backspace returns in upper folder in the tree/ and type again to search.
Not very user friendly and very annoying :-) Now, what should I do? Is there any work around and how can I appropriately file this as a bug?