CascadingDropDown and Method Error 500

To add to my post, I have been looking through the forums about this error. There is a lot of information on it but nothing is working so far.

One of the issues is I can't seem to generate a stack trace of the error. Is there a good way to do that? I'm having issues getting any debug information on this.

Here are the things I've tried.

Default.aspx:
Added EnableEventValidation="false"

App_Code/MenuService.cs:
Change [System.Web.Script.Services.ScriptService] to [System.Web.Script.Services.ScriptService()]
Added using System.Web.Script.Services;
Added static to the method.
Added [ScriptMethod] to the method

I also changed the code to see if it would return a simple value but the same error:

public CascadingDropDownNameValue[] GetShiftsByCostCenter(string sKnownCategoryValues,string sCategory)
 {
 List _lShifts2 =new List();
 _lShifts2.Add(new CascadingDropDownNameValue("test","1"));
 _lShifts2.Add(new CascadingDropDownNameValue("test1","2"));
return _lShifts2.ToArray();
 }

web.config:
Added
<system.web.extensions>
<scripting>
<webServices>
<jsonSerialization maxJsonLength="5000000" />
</webServices>
</scripting>
</system.web.extensions>

Not working yet. Any suggestions are appreciated.

Well this was odd but you don't seem to be allowed to change the definition of the variables.

I had

public CascadingDropDownNameValue[] GetShiftsByCostCenter(string sKnownCategoryValues,string sCategory)

Guess you can't do that. I switched it back.

public CascadingDropDownNameValue[] GetShiftsByCostCenter(string knownCategoryValues,string category)

it works now.