Problem of Mac Mini using with NAS

[JumpJump]

I am the beginner of Mac and just bought a Mac Mini two weeks ago.
My hardware:
Router: Buffalo WHR-G54S
NAS: encore ENNHD-NT (http://www.encore-usa.com/product_item.php)
2 of PC Notebook
1 of Mac Mini 1.83Ghz 1Gram OSx 10.5.3
When I connect all together and share the NAS between PC & MAC, the .jpg file can not be get from the NAS to MAC by finder but PC is work properly. I try to get other type of file from NAS to MAC, it seem unreliable(Someday can copy & someday can not copy).
Remark: The .jpg file on the NAS work properly with the Aperture 2.0 Trial & Lightroom 2.0 Trial. 🙁

 

[ert3]

Um we need more details.

And perhaps using more proper english please.

 

[JumpJump]

I just find problem when I copy the file from NAS to my MAC.
For Jpeg(.jpg) files it just work in the Aperture or Lightroom but can not copy by "finder".
For other files, it is unreliable also in "finder".