Unable to update .MDB file over network using 2008 R2

I have an application that needs to publish PDF's to a network share, and upon doing so this should then update an MDB file located within the same share.

I have a windows 2008r2 server with the program on, this published to my file server, also windows 2008r2. I can publish ok if i log in as a domain admin and then log in as the user, thus it is down to some sort of windows permission that i am not aware of.

The user has full read write access to the share (and this works as they are able to write the pdf and modify the pdf) but they can not change anything on the .MDB file itself (I have checked the file permissions, they are also ok, with the users having full rw access)

any ideas