Inherited Problems

Please bear with me, we have an special case / problem that we have inherited through a new client.

Our client has a website that was built upon Umbraco; an apparently modified version that the origianl developer refuses to provide because it is 'their' code. So, we have an issue where the client is stuck trying to find another developer (us) to help make edits and bare-minimum changes until a new, fresh site can be built.

With that in mind, we have taken a copy of their current Umbraco 4.6.2 installation from their live site, along with a Database backup, and installed them locally on our dev server. This is obviously not an ideal situation, and errors are not a surprise, however i am unable to figure out what this error is telling me:
(Any insight would be much apprciated)

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Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:


An unhandled exception was generated during the execution of the current
 web request. Information regarding the origin and location of the 
exception can be identified using the exception stack trace below.

Stack Trace:


[NullReferenceException: Object reference not set to an instance of an object.]
   umbraco.requestHandler..ctor(XmlDocument umbracoContent, String url) +3695
   umbraco.UmbracoDefault.Page_PreInit(Object sender, EventArgs e) +1217
   System.EventHandler.Invoke(Object sender, EventArgs e) +0
   System.Web.UI.Page.PerformPreInit() +48
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1843

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.18044

Request Details
Session Id:	dnrs3jlqulqq42uzson2qwga	Request Type:	GET
Time of Request:	8/12/2013 9:59:09 AM	Status Code:	500
Request Encoding:	Unicode (UTF-8)	Response Encoding:	Unicode (UTF-8)

Trace Information
Category	Message	From First(s)	From Last(s)
aspx.page	Begin PreInit
umbracoInit	handling request	0.000062	0.000062
request handler	current url ''	0.000237	0.000175
requestHandler	Redirecting to domain: cpt.tsdev.net, nodeId: 4569	0.000371	0.000134
umbracoRequestHandler	xpath: ' \| /root/* [@urlName = ""]'	0.000402	0.000031
umbracoRequestHandler	Just before xPath query (False, ' \| /root/* [@urlName = ""]')	0.000416	0.000015
umbracoRequestHandler	pageXPathQueryStart: '/root'	0.000427	0.000011
umbracoRequestHandler	After xPath query	0.000464	0.000037
umbracoRequestHandler	Access checking started	0.000489	0.000024
Unhandled Execution Error	Object reference not set to an instance of an object. at umbraco.requestHandler..ctor(XmlDocument umbracoContent, String url) at umbraco.UmbracoDefault.Page_PreInit(Object sender, EventArgs e) at System.EventHandler.Invoke(Object sender, EventArgs e) at System.Web.UI.Page.PerformPreInit() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)	0.000612	0.000123

Object reference not set to an instance of an object.

Request Details

Trace Information