Almost forgot to check in:

OpenSim.32BitLaunch.exe is a 32-bit application that loads OpenSim.exe using .Net framework, hence it is JIT-compiled to 32-bit.
Use this app to start OpenSim on 64-bit systems (works great on Vista 64 :))

OpenSim/Region/ScriptEngine/DotNetEngine/Compiler/LSL/Compiler.cs

@@ -273,7 +273,7 @@ namespace OpenSim.Region.ScriptEngine.DotNetEngine.Compiler.LSL
                 case enumCompileType.vb:
                     compileScript = String.Empty +
                                 "Imports OpenSim.Region.ScriptEngine.Common: Imports System.Collections.Generic: " +
-                                String.Empty + "NameSpace SecondLife { " +
+                                String.Empty + "NameSpace SecondLife:" +
                                 String.Empty + "Public Class Script: Inherits OpenSim.Region.ScriptEngine.Common.LSL_BaseClass: " +
                                 @"Public Sub New(): End Sub: " +
                                 compileScript +

OpenSim/Tools/OpenSim.32BitLaunch/OpenSim.32BitLaunch.csproj

@@ -0,0 +1,63 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="3.5" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <ProductVersion>9.0.21022</ProductVersion>
+    <SchemaVersion>2.0</SchemaVersion>
+    <ProjectGuid>{595D67F3-B413-4A43-8568-5B5930E3B31D}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <AppDesignerFolder>Properties</AppDesignerFolder>
+    <RootNamespace>OpenSim._32BitLaunch</RootNamespace>
+    <AssemblyName>OpenSim.32BitLaunch</AssemblyName>
+    <TargetFrameworkVersion>v2.0</TargetFrameworkVersion>
+    <FileAlignment>512</FileAlignment>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>..\..\..\bin\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+    <PlatformTarget>x86</PlatformTarget>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <DebugType>pdbonly</DebugType>
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="System.Xml.Linq">
+      <RequiredTargetFramework>3.5</RequiredTargetFramework>
+    </Reference>
+    <Reference Include="System.Data.DataSetExtensions">
+      <RequiredTargetFramework>3.5</RequiredTargetFramework>
+    </Reference>
+    <Reference Include="System.Data" />
+    <Reference Include="System.Xml" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="Program.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\Region\Application\OpenSim.csproj">
+      <Project>{AC9EB8AB-0000-0000-0000-000000000000}</Project>
+      <Name>OpenSim</Name>
+    </ProjectReference>
+  </ItemGroup>
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
+       Other similar extension points exist, see Microsoft.Common.targets.
+  <Target Name="BeforeBuild">
+  </Target>
+  <Target Name="AfterBuild">
+  </Target>
+  -->
+</Project>

OpenSim/Tools/OpenSim.32BitLaunch/Program.cs

@@ -0,0 +1,10 @@
+namespace OpenSim._32BitLaunch
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            OpenSim.Application.Main(args);
+        }
+    }
+}

OpenSim/Tools/OpenSim.32BitLaunch/Properties/AssemblyInfo.cs

@@ -0,0 +1,36 @@
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+// General Information about an assembly is controlled through the following 
+// set of attributes. Change these attribute values to modify the information
+// associated with an assembly.
+[assembly: AssemblyTitle("OpenSim.32BitLaunch")]
+[assembly: AssemblyDescription("")]
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("Microsoft")]
+[assembly: AssemblyProduct("OpenSim.32BitLaunch")]
+[assembly: AssemblyCopyright("Copyright © Microsoft 2008")]
+[assembly: AssemblyTrademark("")]
+[assembly: AssemblyCulture("")]
+
+// Setting ComVisible to false makes the types in this assembly not visible 
+// to COM components.  If you need to access a type in this assembly from 
+// COM, set the ComVisible attribute to true on that type.
+[assembly: ComVisible(false)]
+
+// The following GUID is for the ID of the typelib if this project is exposed to COM
+[assembly: Guid("5072e919-46ab-47e6-8a63-08108324ccdf")]
+
+// Version information for an assembly consists of the following four values:
+//
+//      Major Version
+//      Minor Version 
+//      Build Number
+//      Revision
+//
+// You can specify all the values or you can default the Build and Revision Numbers 
+// by using the '*' as shown below:
+// [assembly: AssemblyVersion("1.0.*")]
+[assembly: AssemblyVersion("1.0.0.0")]
+[assembly: AssemblyFileVersion("1.0.0.0")]