I am using DNN 4.3.5 and developing custom modules with it.  I am also using AJAX.NET 1.0 and the ControlToolkit in my module.  Everything works with IIS 6.0 running on windows server 2003.  Randomly when trying to browse to my site via http://localhost/[My Install] / it will give me the following error, even though my site was working perfectly fine before (no code changes).

DotNetNuke Upgrade Error
The Assembly Version ( [ASSEMBLYVERSION] ) does not match the Database Version ( [DATABASEVERSION] )

ERROR: Could not connect to database.

An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server).

Here are some things I have found out:

• The MS SQL Server 2005 is still up and running.
• A sql server trace reveals no open connections or connection attempts.
• I am using IIS 6.0 and my site is in its own application pool using .NET 2.0.
• Other sites on this computer are still up and running; even running off the same SQL Server.
• The SQL connection string in my web.config still successfully works using other applications. 

The windows event log gives me the following error:

Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 5/4/2007 7:49:22 PM
Event time (UTC): 5/4/2007 11:49:22 PM
Event ID: 12477364ea3545eea282ca2a64fa9780
Event sequence: 5
Event occurrence: 2
Event detail code: 0

Thread information:
    Thread ID: 1
    Thread account name: NT AUTHORITY\NETWORK SERVICE
    Is impersonating: False
    Stack trace:    at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject)
   at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
   at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
   at System.Data.SqlClient.SqlConnection.Open()
   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.GetPortals()
   at DotNetNuke.Entities.Portals.PortalController.GetPortals()
   at DotNetNuke.Common.Global.CacheMappedDirectory() in d:\inetpub\wwwroot\mysite\App_Code\Global.asax.vb:line 145
   at DotNetNuke.Common.Global.Application_Start(Object Sender, EventArgs E) in d:\inetpub\wwwroot\mysite\App_Code\Global.asax.vb:line 255

Thread information:
    Thread ID: 5
    Thread account name: NT AUTHORITY\NETWORK SERVICE
    Is impersonating: False
    Stack trace:    at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject)
   at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
   at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
   at System.Data.SqlClient.SqlConnection.Open()
   at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteNonQuery(String connectionString, CommandType commandType, String commandText, SqlParameter[] commandParameters)
   at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteNonQuery(String connectionString, CommandType commandType, String commandText)
   at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteNonQuery(String connectionString, String spName, Object[] parameterValues)
   at DotNetNuke.Services.Log.EventLog.DBLoggingProvider.Data.SqlDataProvider.PurgeLog()
   at DotNetNuke.Services.Log.EventLog.DBLoggingProvider.DBLoggingProvider.PurgeLogBuffer()
   at DotNetNuke.Common.Global.LogEnd() in d:\inetpub\wwwroot\mysite\App_Code\Global.asax.vb:line 124
   at DotNetNuke.Common.Global.Application_End(Object Sender, EventArgs E) in d:\inetpub\wwwroot\mysite\App_Code\Global.asax.vb:line 285

The weird thing is, this will last for about 10 or so minutes and then my site will just up and start running again.  It’s a hassle when it happens several times a day. 

So far I have tried the following:

• restarted the IIS service
• stopped/restarted the webpage
• removed my site from the application group and re-added
• restarted the SQL service on the DB server
• recompiled my project
• verified connection string and DB

…. and nothing brings the site back online.  Anyone have any ideas? I’m stuck!  Thanks