reprodukáltam, nálam működik
# ls -ld /pubwrite
drwxrwxrwx 2 root root 72 Dec 15 16:10 /pubwrite
# ls -l /pubwrite
total 4
-rw-r--r-- 1 nobody nogroup 0 Dec 15 16:10 file
-rwxrw-rw- 1 nobody nogroup 9 Dec 15 16:12 marci.txt # ezt Windows-ból hoztam létre

# testparm
[global]
dos charset = 852
unix charset = iso8859-2
workgroup = PROGRAMOZO
server string = %h server (Samba %v)
security = SHARE
passwd program = /usr/bin/passwd %u
passwd chat = *EntersnewsUNIXspassword:* %nn *RetypesnewsUNIXssword:* %nn .
syslog = 0
max log size = 1000
name resolve order = lmhosts host wins bcast
socket options = IPTOS_LOWDELAY TCP_NODELAY SO_SNDBUF=4096 SO_RCVBUF=6
printcap name = /etc/printcap
dns proxy = No
message command = /bin/sh -c '/usr/bin/linpopup "%f" "%m" %s; rm %s'
remote announce = 171.19.193.255 99.99.99.1
invalid users = root
hosts allow = 171.19.192., 171.19.193., 99.99.99.1

[pubwrite]
path = /pubwrite
read only = No
create mask = 0777
directory mask = 0777
guest ok = Yes

Erről jut eszembe: Biztos hogy futtattad a "testparm"-ot az egyes smb.conf módosítások után?