What can be the reason for this error in log viewer:

InnerException: Parser Error: Could not load type 'DotNetNuke.Modules.Admin.PortalManagement.SiteSettings_CMP'.

Last line of exception is:

at DotNetNuke.UI.Skins.Skin.InjectModule(Control objPane, ModuleInfo objModule, PortalSettings PortalSettings)

Where SiteSettings_CMP.ascx is my new control copied from SiteSettings.ascx. I have recompiled the solution many times and no error given, all files are present, namespace is correct, all db entries seems to be correct. So what should I check.

Thanks   

as this is done in core dotnetnuke project so i guess there should not be a problem of assembly. However I am getting this error when i build the solution:

Cannot copy assembly 'Dotnetnuke' to file 'C:\Inetpub\wwwroot\dnn\bin\DotNetnuke.dll'. The process cannot access the file because it is being used by another process.

Is this creating the problem? How can I fix this? I have tried alot but could not.

Vladan Strigo wrote 2. The namespace in the control to the class is not correct

no problem with the namespace, in vb:
Namespace DotNetNuke.Modules.Admin.PortalManagement
and
Public MustInherit Class SiteSettings_CMP
Inherits DotNetNuke.Entities.Modules.PortalModuleBase

in html:
<%@ Control Inherits="DotNetNuke.Modules.Admin.PortalManagement.SiteSettings_CMP" CodeBehind="SiteSettings_CMP.ascx.vb" language="vb" AutoEventWireup="false" Explicit="True" enablev13wstat3="True" targetSchema="http://schemas.microsoft.com/intellisense/ie5" debug="False" %><%@ Control Inherits="DotNetNuke.Modules.Admin.PortalManagement.SiteSettings_CMP" CodeBehind="SiteSettings_CMP.ascx.vb" language="vb" AutoEventWireup="false" Explicit="True" enablev13wstat3="True" targetSchema="http://schemas.microsoft.com/intellisense/ie5" debug="False" %><%@ Control Inherits="DotNetNuke.Modules.Admin.PortalManagement.SiteSettings_CMP" CodeBehind="SiteSettings_CMP.ascx.vb" language="vb" AutoEventWireup="false" Explicit="True" enablev13wstat3="True" targetSchema="http://schemas.microsoft.com/intellisense/ie5" debug="False" %>

Well the "cannot copy...." problem usually occurs when you have multiple referenced assemblies which reference DotNetNuke.dll internally each try to copy it's version of DotNetNuke.dll to the bin directory. The solution is to set to most (if not all) of them (references) the "copy local" attribute to false... then they will not try to put their child dlls in the bin directory.

as for the other problem, do you have maybe the root namespace defined also? if you do you get actually the double namespace to that class.

So, try to solve it in the following way:

1. Check that all dll's that need to go to the bin directory really are deployed there.
2. Check your namespaces (you can take a look at class view to see the complete final path to a certain class)
3. Get your other references in order so that they don't make problems (e.g. DotNetNuke.dll)

hope it helps,