storage server 2003 nfs problem

i have to move the mail forlder of our server to a windows storage server 2003 nfs share.

our mail server is a qmail on a linux gentoo.

we use maildir format.

the problem is that when i try to copy message from domains folder to the mounted
share i got an error for some (a lot of) message: cannot create regular file

i thougth the problem was in the name, but it seems to me that file with similiar names give no error at all.
what can i do to solve this ?

example:
plutone vpopmail # cp -rp domains/xxxx.xx/* domain2/xxxx.xx/
cp: cannot create regular file `domain2/xxxx.xx/xxxxx/.maildir/.Sent/cur/1095276122.M653035P8852V0000000000000901I000534A2_0.plutone,S=2840:2,S': Invalid argument
cp: cannot create regular file `domain2/xxxx.xx/xxxxx/.maildir/.Sent/cur/1113657857.M927355P32214V0000000000000901I001C362C_0.plutone,S=2035:2,S': Invalid argument