error 64 The specified network name is no longer available.

Hi , I am trying to copy files from windows xp pc to dell rs 730 server which is running on windows 2003 sp2. every 1.5 secs i am trying to copy file.

after some time ( some times within hour some times after 6 or 7 hours) i am seeing some buch of files are not copied with error 64.

Can you please let me know what can be the problem and how to solve it

Thanks in advance