Could not find a part of the path ' ' ...while uploading file from client machine.

Hi...

I have developed a web part to upload images to SharePoint 2010 picture library.

It's works fine when I tried to upload form server machine where SharePoint is deployed, but error Couldnot find a part of the path '........ ' occurs when user try from their local machines. 

What can be the issue ? Please help.

Regards,

Mehar