Some users unable to access shares in AD environment

I have a fairly new windows 2003 file server. It is a member of our AD domain and the only role it has is file server. I have created the folders and gave the right people access to their folders. some people can access their folders from a mac or pc, some from only a pc and some can’t get in period. Some that could access them from a mac 2 weeks ago now can’t access it period. I have deleted the users from the permissions and readded and had the AD accounts checked to make sure they are not locked. Can anyone offer any advice???