How to change permissions on mounted windows share?

I changed my /etc/fstab to:

//server/share  /media/share  cifs  username=msusername,password=mspassword,uid=1000,gid=1000  0  0

Your entry in fstab is creating the mount point in /mnt. Using the /mnt directory should only work if the drive is a local volume rather than a network share or removable device.

Edit your fstab entry to:

//servername/sharename  /media/ussenterprise  cifs  username=msusername,password=mspassword,umask=002,uid=1000,gid=1000,iocharset=utf8,sec=ntlm  0  0

This assumes that your uid and gid are 1000 which is the first default user and group IDs. Then use:

sudo umount /media/ussenterprise
sudo mkdir /media/ussenterprise
sudo chown user:user /media/ussenterprise
sudo chmod 755 /media/ussenterprise
mount -a

This should mount the share with your user ID and permissions set to read/write.

Try these options:

username=msusername,password=mspassword,iocharset=utf8,sec=ntlm,nosetuids,noperm

(definitions of noperm and nosetuids are found in the mount.cifs manpage)

Also, think about using a credentials file instead of having your name/pw in the clear:

credentials=/home/<user>/.smbcredentials

since fstab can be read by all.