I have a DNN site which was originally installed at 5.6.1 and then upgraded to 5.6.2. I have just installed the document module on a page for the first time and I cannot get any version to work - as soon as I go into settings I get the 'Critical Error, object reference not set' error.  Here's the event log content:

AssemblyVersion: 5.6.2
PortalID: 0
PortalName: Eversure
UserID: 1
UserName: webmaster
ActiveTabID: 70
ActiveTabName: Datasheet Management
RawURL: /Admin/DatasheetManagement/tabid/70/ctl/Module/ModuleId/425/Default.aspx
AbsoluteURL: /Default.aspx
AbsoluteURLReferrer: http://www.eversure.com.au/Admin/DatasheetManagement.aspx
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.17) Gecko/20110420 Firefox/3.6.17 ( .NET CLR 3.5.30729)
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: 1bc26e94-6ec8-4a62-b35f-ac1f66426edb
InnerException: Object reference not set to an instance of an object.
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: DotNetNuke.Modules.Documents.EditDocumentsSettings.Page_Load
StackTrace:
Message: DotNetNuke.Services.Exceptions.PageLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object. at DotNetNuke.Modules.Documents.EditDocumentsSettings.Page_Load(Object sender, EventArgs e) at System.Web.UI.Control.OnLoad(EventArgs e) at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace ---

I have followed all the steps referenced in this thread - I have downloaded all of versions 4.1.0, 4.1.1 and 4.1.2 from Codeplex, installed each of them individually, purging all files and table entries between each attempt. I have installed 4.1.0 and upgraded to 4.1.1 and 4.1.2, both stepwise via 4.1.1 and direct to 4.1.2 from 4.1.0, as recommended in the note on the Codeplex download page.  Nothing I do can get the damn thing to work.  This is super-urgent - please advise how I can get this module to function.

If you need get a login to the site to assist please contact me via support at epicservices dot com dot au

Thank you very much for suggesting a way to solve this problem, documents module worked.