Navigation bar moves right when changing image in a skin (CRM 7.0)

Hello friends, I have an issue on CRM 7.0 WebClient

I copied the standard BSP that handles the standard skins into my own namespace

I define a new skin (copied from 'Default') and its path in Customizing for Skin.

I upload and replace an "Z" skin for my own image ".gif" that is EXACTLY the same shape and name as the original. So far so good....

However, when I open the skin, the image gets loaded, but the entire navigation bar goes right and the whole screen layout gets disarranged and of course it becomes unusable. Very weird right? No idea what happened because the image has the same name and size than the standard one I replaced

I would like to know how to solve this issue, Thanks and regards from Martin.