I just set up a samba server today and I ended up having similar problems.
Did you use Fedora's GUI tool or did you manually configure it? Are you having this problem from just your linux machine and are you able to write using the Windows machines? How are you trying to access and write to the share? (I.E. linux command-line, windows explorer, konqueror, nautilus, etc....) What error messages did you get?
This is fresh in my mind from merely hours ago:
On the linux side, the folder that I mounted to with smbmount (you can use mount -t smbfs or mount.smbfs... it's all the same) it had to be done as root and therefore the folder in which the share is mounted became owned by root.root and not username.users. It caused the folder to be read-only for everyone and writable only by root. I passed -o rw,uid=###,gid=### to the mount command to make sure that it was mounted for my username ownerships. You can get those ownerships by doing:
grep <username> /etc/passwd
and third and fourth fields are your uid and your gid respectively. What also helped for me was that the actual folders on the server that are being shared had permissions of drwxrwx--- (chmod 770).
The other thing you want to do with your level of security is make sure that the usernames match. If the passwords don't then you should be prompted but as long as the usernames match you shouldn't have a problem. Either that or allow for the use of a guest account if a username can't be matched... you haven't set that up so I'm assuming that's not a road you'd like to travel. I only mention it because public = yes is in your share options so it's possible you can see your stuff but you can't write to it because you aren't logged in.
EDIT: Each user needs an account on the server itself which is added to to samba either through the GUI tool or the smbpasswd command.
One thing I just can't help you with is SELinux. Google around or search here for SELinux Samba or something and see if you can trace some symptoms but without knowing any specifics I do know that SELinux can sometimes cause grief if left alone.
If you check out the Samba-3 HOWTO
you'll get some fantastic information. What I did was I started here
and modified the smb.conf file option by option as I read on and testing the network after each modification. I learned a lot and it works pretty well but I'd recommend some patience and a "can-do" attitude. Take into account that Fedora does things a little differently.
I'm not a Samba guru so without more information I can't help you much more right now. That and I'm quite tired. Good luck and let us know how you make out.