User Interface for Document Managment System

I'm working on a Document Managment System and i'm trying to figure out the best layout for the UI.
The system has a dynamic category system, meaning that you may add any number of nested categories.  Any one of these categories may contain other categories and documents.  Documents consist of a little bit of info about it, and any number of files maybe associated with it.

This was my first idea.
___________
| Add New |
-----------
       | Currently Selected CatName |
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| Docs | CatName1 | Cat Desc1 | Edit/Delete |
| Docs | CatName2 | Cat Desc2 | Edit/Delete |
| Docs | CatName3 | Cat Desc3 | Edit/Delete |
| Docs | CatName4 | Cat Desc4 | Edit/Delete |
| Docs | CatName5 | Cat Desc5 | Edit/Delete |
---------------------------------------------

Add new is a link to create a new category
then the caption above the table would be the name of the current category, or a 'bread crumb' link.
Each record is a category that exist in the currently selected category.
Clicking on the CatName field would update the table to contain the subcategories of that category
Docs is a link to a page that list all of the Documents in that category which would basicly look like the above table, except the Docs link would be Details, or something and clicking it would take you to a DocumentDetails page that showed the Document info a dn listed the files that are associated with it.

The other idea I had was to get rid of the Docs link altogether and put the Categories and Documents table on the same page since they both use the Currently selected category to figure out what to diplay.

i've also considered using a layout that has a menu on the left that shows the categories and using the left side of the page to display Documents and Document Details.

What do you think would be the best layout?  Is there another layout that might be better? Any ideas, would be greatly appreciated...