Network Access Storage (NAS)?

I have a NAS Unit on my home network, with My Documents etc saved on this NAS. On my laptop (W7), I have linked to the NAS via the "make available offline" facility in W7. I have also mapped U: to the NAS My Documents. Norton Online Backup does not count any files in either of these network connection methods. Am I doing something wrong, or does Norton On-line Backup not suppoer NAS access? If not, then I have purchased 25GB for nothing!!! NAS is becomong more popular in a home environment. What do you suggest?