Ubuntu :: No Write Permission Even Though User Is Member Of Folder Group?

I'm having an odd problem (although I'm probably missing something obvious to a non-semi-newbie):I have a directory used for samba shares which is owned by user fred, a system user which the windows clients on my network authenticate with to access the shares. I, roger, want to access the directories without having to put my 'sudo boots' on every time, so I made the directory group users and added roger to that group, and changed the file/folder modes from 0755 to 0775.However I still do not have write permissions inside the directory; I still seem to be considered 'other' and hence only have read and execute.