I changed the web.config files customErrors to Off and now I get the following error, your help is much appreciated.
Server Error in '/' Application.
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Required permissions cannot be acquired. 
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.Security.Policy.PolicyException: Required permissions cannot be acquired.
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: 
[PolicyException: Required permissions cannot be acquired.]
   System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Boolean checkExecutionPermission) +2770052
   System.Security.SecurityManager.ResolvePolicy(Evidence evidence, PermissionSet reqdPset, PermissionSet optPset, PermissionSet denyPset, PermissionSet& denied, Int32& securitySpecialFlags, Boolean checkExecutionPermission) +57
[FileLoadException: Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging.Configuration.Design, Version=3.1.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. Failed to grant minimum permission requests. (Exception from HRESULT: 0x80131417)]
   System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) +0
   System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) +54
   System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +211
   System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +141
   System.Reflection.Assembly.Load(String assemblyString) +25
   System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +32
[ConfigurationErrorsException: Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging.Configuration.Design, Version=3.1.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. Failed to grant minimum permission requests. (Exception from HRESULT: 0x80131417)]
   System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +596
   System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory() +211
   System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +46
   System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +177
   System.Web.Compilation.BuildProvidersCompiler..ctor(VirtualPath configPath, Boolean supportLocalization, String outputAssemblyName) +185
   System.Web.Compilation.CodeDirectoryCompiler.GetCodeDirectoryAssembly(VirtualPath virtualDir, CodeDirectoryType dirType, String assemblyName, StringSet excludedSubdirectories, Boolean isDirectoryAllowed) +350
   System.Web.Compilation.BuildManager.CompileCodeDirectory(VirtualPath virtualDir, CodeDirectoryType dirType, String assemblyName, StringSet excludedSubdirectories) +125
   System.Web.Compilation.BuildManager.CompileCodeDirectories() +525
   System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled() +448
[HttpException (0x80004005): Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging.Configuration.Design, Version=3.1.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. Failed to grant minimum permission requests. (Exception from HRESULT: 0x80131417)]
   System.Web.Compilation.BuildManager.ReportTopLevelCompilationException() +57
   System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled() +612
   System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters) +644
[HttpException (0x80004005): Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging.Configuration.Design, Version=3.1.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. Failed to grant minimum permission requests. (Exception from HRESULT: 0x80131417)]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +3465427
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +69
   System.Web.HttpRuntime.ProcessRequestInternal(HttpWorkerRequest wr) +279
 
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Version Information: Microsoft .NET Framework Version:2.0.50727.1433; ASP.NET Version:2.0.50727.1433