I set my debug flag to TRUE and custom error mode to OFF and received the following:

Server Error in '/' Application.

---

Access to the path 'C:\Inetpub\******\dspwest.com\httpdocs\Install\UnderConstruction.htm' is denied.

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.UnauthorizedAccessException: Access to the path 'C:\Inetpub\******\dspwest.com\httpdocs\Install\UnderConstruction.htm' is denied.

ASP.NET is not authorized to access the requested resource. Consider granting access rights to the resource to the ASP.NET request identity. ASP.NET has a base process identity (typically {MACHINE}\ASPNET on IIS 5 or Network Service on IIS 6) that is used if the application is not impersonating. If the application is impersonating via <identity impersonate="true"/>, the identity will be the anonymous user (typically IUSR_MACHINENAME) or the authenticated request user.

To grant ASP.NET access to a file, right-click the file in Explorer, choose "Properties" and select the Security tab. Click "Add" to add the appropriate user or group. Highlight the ASP.NET account, and check the boxes for the desired access.

Source Error:

Line 106:            If Not File.Exists(System.Web.HttpContext.Current.Server.MapPath("~/Install/UnderConstruction.htm")) Then
Line 107:                If File.Exists(System.Web.HttpContext.Current.Server.MapPath("~/Install/UnderConstruction.template.htm")) Then
Line 108:                    File.Copy(System.Web.HttpContext.Current.Server.MapPath("~/Install/UnderConstruction.template.htm"), System.Web.HttpContext.Current.Server.MapPath("~/Install/UnderConstruction.htm"))
Line 109:                End If
Line 110:            End If

[UnauthorizedAccessException: Access to the path 'C:\Inetpub\******\dspwest.com\httpdocs\Install\UnderConstruction.htm' is denied.]
   System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) +2013027
   System.IO.File.InternalCopy(String sourceFileName, String destFileName, Boolean overwrite) +488
   System.IO.File.Copy(String sourceFileName, String destFileName) +6
   DotNetNuke.Common.Global.CreateUnderConstructionPage() in C:\Inetpub\******\dspwest.com\httpdocs\App_Code\Global.asax.vb:108
   DotNetNuke.Common.Global.CheckVersion() in C:\Inetpub\******\dspwest.com\httpdocs\App_Code\Global.asax.vb:91
   DotNetNuke.Common.Global.Application_Start(Object Sender, EventArgs E) in C:\Inetpub\******\dspwest.com\httpdocs\App_Code\Global.asax.vb:263

Version Information: Microsoft .NET Framework Version:2.0.50727.42; ASP.NET Version:2.0.50727.42