This is a major flaw and Apple seems to be totally uninterested in sorting this out.
A long term Windows user - now been using Mac for 3 years - this has been a constant problem - with no solution that doesn't involve continuously tinkering under the bonnet and doing the same things over and again.
I am the sole user of my Mac - and am, therefore, the admin and should have full permissions for everything. I have a NAS on my home network - Windows accesses this with no problems (all permissions are correctly setup on the NAS). Can OS X deal with it properly - of course not! I am constantly running into a brick wall with permissions - telling me I don't have the correct permissions. OS X seems happy to change these randomly - what was read & write is now read only. Ridiculous. I am then not, as the admin, allowed to change them - being told I don't have the right permissions to do this.
This is a fundemental issue that needs addressing - Apple have not over the past 3 years of my experience and I don't expect they will in the future. The most advanced OS? Laughable.
Of course, following vaious threads requires the end user to either mess around in Terminal or play around with Disk Utility - both not dealing with my own files on my own NAS!