Image files detach when a colleague opens my drawing and vice verse

Can any one shed a light on why when I create a drawing and attach an image file (jpeg or tiff), and I can come in and out of the drawing and everything works fine. However when my colleague later opens the same drawing he has to re-map the image files and vice verse.

We are both using Autocad 2011, the drawings and images are saved to the same place on the company network with the same file paths and drive names but when I open a drawing he last worked on or he a drawing I last worked on the images detach.

The only difference I can possibly think of is that I am using windows7 and he isn't.

Does anyone have any ideas, it's driving us nuts as most of drawings contain image files.

Are they full path, relative path or no path?

Yes full path.

Put the images in the same exact folder as the dwg and it will load no matter what the path is.

Whereas putting the image files in the same directory as the dwg file does work this is not a practicle solution as we have hundreds of these files which are maps covering the whole of the UK and so copying or moving files to the same diretories would take up too much time and space on the network and things would get too messie trying to keep track of what is where etc.

Operating in a mixed Windows OS environment should have little or nothing to do with the behavior you are experiencing IMO.

My basis - My team converted to Windows 7 64-Bit 4-6 months prior to all other users in my office of +/-80 staff, in our region of +/-600 staff, in my country, etc., etc.... at no time did any behavior such as this pop up while working with other teams who were still using Windows XP 32-Bit.

Would it be possible for you to confirm that the fellow coworker is in fact using the same standard company defaults (i.e., AutoCAD Profile, ACADDOC.lsp, etc.)? It sounds to me as if there is either custom code executing (be it by intent on their part, or as a prank on the part of someone else?), or that there may be something wrong with their installation.

Do images detach for only this one coworker, or are there others that experience this behavior also?

What is the name of the path? It should start with the Drive Letter:\Folder1\Folder2\Image.tif (G:\MAP\IMAGES\MyImage.tif)