SAME Here, I have reinstalled several times, Went back a couple versions then upgraded. All went well until I click on the login button
I get the error

A critical error has occurred.
web.config(24): error CS0138: A using namespace directive can only be applied to namespaces; 'System.Configuration.ConfigurationManager' is a type not a namespace

The Event Log is as Below:

Event Type: Warning
Event Source: ASP.NET 2.0.50727.0
Event Category: Web Event
Event ID: 1309
Date:  6/26/2008
Time:  11:41:35 AM
User:  N/A
Computer: HCWEBB
Description:
Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 6/26/2008 11:41:35 AM
Event time (UTC): 6/26/2008 3:41:35 PM
Event ID: 0aeac505bb904c7d8fe695e74502d1c0
Event sequence: 6
Event occurrence: 1
Event detail code: 0
 
Application information:
    Application domain: /LM/W3SVC/2018729876/Root/HG-41-128589684146268901
    Trust level: Full
    Application Virtual Path: /HG
    Application Path: C:\Inetpub\wwwroot\NEWHG\
    Machine name: HCWEBB
 
Process information:
    Process ID: 2632
    Process name: w3wp.exe
    Account name: NT AUTHORITY\NETWORK SERVICE
 
Exception information:
    Exception type: SqlException
    Exception message: Could not find stored procedure 'dbo.GetHostSettings'.
 
Request information:
    Request URL: 
    Request path: 
    User host address: 
    User: 
    Is authenticated: False
    Authentication Type: 
    Thread account name: NT AUTHORITY\NETWORK SERVICE
 
Thread information:
    Thread ID: 16
    Thread account name: NT AUTHORITY\NETWORK SERVICE
    Is impersonating: False
    Stack trace:    at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
   at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
   at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()
   at System.Data.SqlClient.SqlDataReader.get_MetaData()
   at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
   at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior)
   at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteReader(SqlConnection connection, SqlTransaction transaction, CommandType commandType, String commandText, SqlParameter[] commandParameters, SqlConnectionOwnership connectionOwnership)
   at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteReader(String connectionString, CommandType commandType, String commandText, SqlParameter[] commandParameters)
   at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteReader(String connectionString, CommandType commandType, String commandText)
   at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteReader(String connectionString, String spName, Object[] parameterValues)
   at DotNetNuke.Data.SqlDataProvider.GetHostSettings()
   at DotNetNuke.Entities.Host.HostSettings.GetHostSettings()
   at DotNetNuke.Services.Scheduling.SchedulingProvider.get_SchedulerMode()
   at DotNetNuke.Services.Scheduling.DNNScheduling.Scheduler.CoreScheduler.Halt(String SourceOfHalt)
   at DotNetNuke.Services.Scheduling.DNNScheduling.DNNScheduler.Halt(String SourceOfHalt)
   at DotNetNuke.Common.Initialize.StopScheduler()
   at DotNetNuke.Common.Global.Application_End(Object sender, EventArgs e)
 
 
Custom event details:

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

THIS IS DRIVING me NuTS

....hmm

I reinstalled yesterday and it didn't go haywire overnight. It still seems to be running fine. The only thing that changed between the two installs was that I didn't add a handful of optional modules yesterday. (documents, events, store)

Today I went ahead and installed those modules, and then made sure I had the latest version of those with later versions. We'll see if the installation goes down overnight tonight.

Nothing makes me more nervous than a serious technical problem that mysteriously solves itself. I would hate to go into production and then wake up one morning with a bunch of hosting customers angry at me because the whole installation went down due to a mystery bug.