Project Properties

Error: There was an error trying to load project properties window. Close the window and try again.
Object reference not to an instance of an object.

If you have this error and you can't load project properties and etc... Don’t worry! Because you have chance for continue your tasks without solving this error.
For example if you want to change your application's icon you must edit a XML base file in an editor (like notepad).
Go to your project directory and open [projectname].csproj (for example like WindowsApplication1.csproj) in notepad or any simple text editor.
You can see a part of a TEXT in XML format like below:

<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<Configuration Condition="'$(Configuration)' == '' ">Debug</Configuration>
<Platform Condition="'$(Platform)' == '' ">AnyCPU</Platform>
<ProductVersion>8.0.40607</ProductVersion>
<SchemaVersion>2.0</SchemaVersion>
<ProjectGuid>{CDBB5C9E-C36D-489B-A538-6FD750DE8CBC}</ProjectGuid>
<OutputType>WinExe</OutputType>
<RootNamespace>WindowsApplication1</RootNamespace>
<AssemblyName>WindowsApplication1</AssemblyName>
<WarningLevel>4</WarningLevel>
<ApplicationIcon>app.ico</ApplicationIcon>
...

You can see the <ApplicationIcon>app.ico</ApplicationIcon> that can solve your Application Icon problem without loading the project properties page.
This XML file is so simple and you can solve more other problems with a little search;-)
After that, you must load your solution and compile it again.
This method is for Visual Studio Project 2005 (Whidbey) but absolutely can used for VSP2002 and VSP2003 and VSP2005Beta2 and I think that can be also used for Orcas (next generation of Visual Studio)
The mentioned points are for C# project but absolutely not different for VB.Net, J# and other .Net projects.