I had the same problem before..it does seem that when it is running in the server it cant locate it if you just input the mapped drive..i solved this by just giving the complete path..on my case in the office its something like this:
I had the same problem too.
I solved in two ways:
(Attention at the folder security.) I used this in script.
(Attention at the folder security.
Attention at map networking drive.) I used this in vbs macro.