Hi… in which table are the group memberships for users via LDAP stored?
Links between LDAP users and Matrix group are in sq_shdw_ast_lnk.
Links between LDAP users and LDAP groups are only stored in the LDAP directory. Matrix queries it as required.
Thanks.
If on Active Directory i have setup a group of users, can i export that group to matrix, and assign permissions on that group?
If you have existing groups of users in AD, you can assign them permissions and use them in workflow, just as you would with normal Matrix groups. You find the group by browsing the AD in the asset map and then select it when picking groups.
thats what i want, however it's not working that way 
I setup a global security group in AD, and assiged a user to it (just to test)
then i set up a page with read access to only that group, (and no public). when i try to browse the page, i log in with that user in the group, and i get message that it did log me, but i don't have access to the page.
Any idea?
To get group membership for a user, we look in the memberof attribute of the user (or whichever attribute you have configured on the LDAP User Setup screen). Can you check your User Setup to see which attribute is being used and make sure the user has the group's DN in that attribute.
AD have a "Primary Membership" that isn't usually exposed in the memberOf attribute. You should check that your AD group is visible in the memberOf attribute exposed for that user.