Why can't I access a directory that I should have access to by group? My user belongs to the group www-data, and the directory has permissions granted for this group. But I cannot access it.
markus@hemulen:~$ ls -la
drwxrwx--- 2 www-data www-data 4096 2009-10-11 21:28 test
markus@hemulen:~$ groups markus
markus www-data admin
markus@hemulen:~$ cd test
-bash: cd: test: Permission denied
try just "groups" without "markus", to see if the current shell knows the groups you belong to.
If you just added yourself to the group, you have to log out and log back in again to get the change to apply. I've been caught by that many times...