Class library projects organisation

I have many classes that will be used in many websites and applications.

Some of these classes depend on eachother, but there are no circular dependencies (yet, would this be an issue if there ever were?).

Currently they are all in the same project which creates one DLL.

I want to seperate some of the classes out so that they each get their own DLL, but i want to keep all classes in each of the DLLs in the same namespace.

I think i've achieved this by having seperate projects with their 'default namespace' property set to my desired NS and adding the namespace NS {...} in the code files. I've crated a solution that contains these projects too.

The problem i'm having seems to come from all the references to eachother.

When i create a new web app that will require references to all of these dlls i it uses old versions. I've doing 'update reference' in the web app for each DLL, and also doing the same for each dll in each project for each of the classes but it still seems to be picking up the wrong version from somewhere.

Any idea what i'm doing wrong? or am i going about this completely the wrong way?