Why folders keep shifting their positions?

I bought a new MacBook Pro 15-inch model with highest specifications in this June. I also installed newest version of Mac OS X, Lion (updated).

Yesterday, I turned on my computer and noticed that some of the folders on my desktop were rearranged. Today, the same thing happened again. I would like to ask you what the possible problem could be?

I did not touch any of the ".DS_Store" files.

If you do not have auto arrange turned on (and it says "Arrange by: None", please try the following things.

1) If you are only experience problems on the Desktop, but not in any other finder window, please delete the preference file com.apple.desktop.plist from your user/library/preferences folder

2) If that does not solve problem, delete the .Ds_Store files in any folders you are having problems with, including the Desktop and let Lion recreate them

3) Lastly, as I mentioned in your other thread, this does seem to be a known problem in Lion. Please keep an eye on this thread and this thread for other solutions and/or possible resolution in a future Lion update.