Assuming both your Windows client and Isilon server are set up on the AD domain correctly,
Access on Isilon is controlled at the 'share level' and at the 'filesystem level'. It sounds like you have granted wide-open access at the share level and my guess is the file system permissions are blocking you.
If the directory you are trying to share is /ifs/test_share_dir you might see something like this from the CLI.
# ls -led /ifs/test_share_dir
drwxr-xr-x 2 root wheel 0 Jan 19 15:10 /ifs/test_share_dir
OWNER: user:root
GROUP: group:wheel
SYNTHETIC ACL
0: user:root allow dir_gen_read,dir_gen_write,dir_gen_execute,std_write_dac,delete_child
1: group:wheel allow dir_gen_read,dir_gen_execute
2: everyone allow dir_gen_read,dir_gen_execute
The lines beginning with 0, 1, and 2 are the FACLs. Add a FACL for your userid or group in the 'zeroth' position
# add userid permission to shared directory.
chmod +a# 0 user "MYDOMAIN\myuserid" allow dir_gen_all,object_inherit,container_inherit /ifs/test_share_dir
# or add group permission to shared directory
chmod +a# 0 group "MYDOMAIN\My Admin Group" allow dir_gen_all,object_inherit,container_inherit /ifs/test_share_dir
You should then be able to access the share from windows and use Explorer to adjust permissions to suit.
-Scott