I performed an upgrade to 4.08.04 i had issues with a few things and the forums were very helpful i dind't see a solution to the problem I am having now.

When i try to delete a portal i recieve the message below.  Please help!

Error: Portals is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression. The statement has been terminated. ---> System.Data.SqlClient.SqlException: Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression. The statement has been terminated. 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.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.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) at System.Data.SqlClient.SqlCommand.ExecuteNonQuery() at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteNonQuery(SqlConnection connection, CommandType commandType, String commandText, SqlParameter[] commandParameters) at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteNonQuery(String connectionString, CommandType commandType, String commandText, SqlParameter[] commandParameters) at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteNonQuery(String connectionString, String spName, Object[] parameterValues) at DotNetNuke.Data.SqlDataProvider.DeletePortalInfo(Int32 PortalId) at DotNetNuke.Entities.Portals.PortalController.DeletePortalInfo(Int32 PortalId) at DotNetNuke.Entities.Portals.PortalController.DeletePortal(PortalInfo portal, String serverPath) at DotNetNuke.Modules.Admin.Portals.Portals.grdPortals_DeleteCommand(Object source, DataGridCommandEventArgs e) --- End of inner exception stack trace ---

I checked the Tables there is no duplicate portal ID.  This was also a portal i recently created.  I also tried to delete an old portal and received the same message.  The directory was deleted form WEBROOT of DNN as well as IIS entries just not the database entries.   I don't notice any other issues such as updating portals/portal alias work fine and creating portals works fine.  Below is my portal home directories I'm trying to delete portal please let me know what more i can check and provide to assist in resolving.

Home Directory
Portals/0
Portals/49
Portals/2
Portals/4
Portals/5
Portals/12
Portals/8
Portals/10
Portals/11
Portals/52
Portals/14
Portals/16
Portals/17
Portals/19
Portals/20
Portals/38
Portals/40
Portals/23
Portals/25
Portals/27
Portals/42
Portals/31
Portals/45
Portals/46
Portals/47
Portals/28
Portals/48
Portals/50
Portals/51
Portals/53
Portals/57
Portals/58
Portals/59
Portals/61
Portals/72
Portals/73
Portals/74
Portals/75
Portals/68
Portals/44
Portals/56
Portals/71
 

I had this happen just once a couple years ago and the cause was just as Sebastian indicates. When you say you checked for duplicates in the table, do you mean that you ran something like "select portalaliasid from portalalias order by portalaliasid" in Host/SQL and didn't find a duplicate ID? If you did it indirectly through some other means, you still might have a duplicate entry in the table itself and be overlooking the root cause.