We have dotnetnuke site for a while, then all of sudden, we got the following error when launch the site:

Server Error in '/' Application.
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Input string was not in a correct format.
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.FormatException: Input string was not in a correct format.

Source Error:

Line 229:                Me.SiteLogHistory = IIf(IsDBNull(result("SiteLogHistory")), -1, result("SiteLogHistory"))
Line 230:                Me.AdminTabId = result("AdminTabId").ToString
Line 231:                Me.SuperUserId = result("SuperUserId").ToString
Line 232:                Me.SuperTabId = result("SuperTabId").ToString
Line 233:
 

Source File: C:\Inetpub\wwwroot\reseller\Components\Configuration.vb    Line: 231

Stack Trace:

[FormatException: Input string was not in a correct format.]
   Microsoft.VisualBasic.CompilerServices.DoubleType.Parse(String Value, NumberFormatInfo NumberFormat) +195
   Microsoft.VisualBasic.CompilerServices.IntegerType.FromString(String Value) +97

[InvalidCastException: Cast from string "" to type 'Integer' is not valid.]
   Microsoft.VisualBasic.CompilerServices.IntegerType.FromString(String Value) +212
   DotNetNuke.PortalSettings.GetPortalSettings(Int32 tabId, String PortalAlias) in C:\Inetpub\wwwroot\reseller\Components\Configuration.vb:231
   DotNetNuke.PortalSettings..ctor(Int32 tabId, String PortalAlias, String ApplicationPath) in C:\Inetpub\wwwroot\reseller\Components\Configuration.vb:185
   DotNetNuke.Global.Application_BeginRequest(Object sender, EventArgs e) in C:\Inetpub\wwwroot\reseller\Global.asax.vb:128
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute() +60
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +87

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Version Information: Microsoft .NET Framework Version:1.1.4322.2032; ASP.NET Version:1.1.4322.2032

Any advice is appreciated.

Thanks