Version:           1.6.1 (using KDE 4.6.4) 
OS:                Linux

i've only tried this in the columns view mode.

this seems to only happen if the opened-by-hovering folder is a subfolder of an ancestor folder of the containing folder of the file that is being dragged.  for example, in the following tree:

aa/
+ ao/
  + aoe/
+ ae/
  + aeu/
  + file1

the issue is triggered by dragging file1 to any folder except aa, ae, and aeu.  it is assumed that the top level of the columns view is at aa or higher.

Reproducible: Always

Steps to Reproduce:
1. in Dolphin's Navigation settings, enable "Open folders during drag operations".
2. set Dolphin to use the columns view mode.
3. navigate at least one level deep below the top level column's folder.
4. drag a file from that level.
5. hover over a folder in a higher level until it opens.
6. drag the file over the just-opened folder's column.

Actual Results:  
dropping the file has no effect in any column.

Expected Results:  
dropping the file works as it would otherwise.

OS: Linux (x86_64) release 2.6.38-10-generic
Compiler: cc