Thanks for the help. this is most likely the reason I am having this problem. I have the service set up to run as the user with read/write access to the share/drive.
I also understand that the UNC path has it's merits. My problem is that we use a lot of different automated jobs here, and the IT/Server people occassionall move things around. If I use drive letters in the code then I don't have to change every script running on a given server every time a share is moved to a new machine or changed. I just need to change the mapped drive.
I suppose I will just need to mark down this special case and make sure someone remembers it next time the server changes.
thanks