If it were a general network issue I would not expect it to always error at the same location.
The first thing I would suggest looking at is access rights. The user account used for accessing the network share might have the right to read the directory (and so see the file exists) but not access the file itself at all. It could also be that the file is locked by another process elsewhere. While both of these issues would normally result in an explicit "permission denied" error condition, depending on the network file access protocol you are using the condition could be being misreported.
Another possibility is that the path is too long for something along the way to handle - the example you give implies that the directory structure is quite deep. What protocols are you using and how long is the real path to the file? Does the operation succeed for files with the same or longer full path?