hi
I have same problem. search very much,try any way but no solution find yet. i thinks this problem would solve in v 6beta3.may be should try. http://www.mikrotik.com/download/CHANGELOG_6
i was have this problem b4 but i found that u must make profile in user manger so u can sign in to internet by hotspot or pppoe / again dont forget to make profile in usermanger to the users