I have a Windows XP machine sharing the folder "share19".

It is mounted in Lubuntu 12.04 adding the next line to fstab:

// /home/paul/folder cifs username=win_user,password=win_pass,iocharset=utf8 ,mode=0777,dir_mode=07*​77 0 0

The user "paul" is a common user, not root, not sudoer, not nothing.

Loged like "paul" i can access to the share, create files and delete files but can't modify them.
I create a LibreOffice spreadsheet, but after close LibreOffice when i tried to re-open the spreadsheet, it opens in Read-Only mode. Same thing in the terminal with nano and plain-text files.

If i logon with the sudoer user and run programs with sudo, NO problem.

From machines with regular Ubuntu or Windows there's no problem neither.