i have a directory with drwx------ perms and there is a sub dir with drwxr-xr-x perm which i cannot access (when not owner)... why??

I believe permissions are heirarchial. So if you don't have access to the parent directory, you won't have access to the child directory either, no matter what the permissions say.

Indeed, pljvaldez, but this hierarchy is based on the "x" (execute) permission bit of the directory.

Directory permissions are:
r => read the contents of the directory (ie the names of the files/subdirs)
w => add/remove files/subdirs
x => search: this allows you to try to access a subdirectory (with it's own permissions)
So, if you don't have x permission, you can't access the subdirectory.

Whenever you access a file / directory by specifying it's full path, all the parent directories (leading up to /) must have "x" bit set.

A hint: please be carefull when setting file/directory permissions, as they are vital to your computer's security.