Help!

I am running version 4.5.1. A moment ago, I was browsing my portal and I got a generic .NET error page. I logged onto my server, and this is the error:

Index was outside the bounds of the array.

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.IndexOutOfRangeException: Index was outside the bounds of the array.

Source Error:

[IndexOutOfRangeException: Index was outside the bounds of the array.]
   System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) +992837
   DotNetNuke.Entities.Tabs.TabController.FillTabInfo(IDataReader dr, Boolean CheckForOpenDataReader) +2049
   DotNetNuke.Entities.Tabs.TabController.GetTab(Int32 TabId, Int32 PortalId, Boolean ignoreCache) +225
   DotNetNuke.Entities.Portals.PortalSettings.VerifyPortalTab(Int32 PortalId, Int32 TabId) +403
   DotNetNuke.Entities.Portals.PortalSettings.GetPortalSettings(Int32 TabId, PortalAliasInfo objPortalAliasInfo) +2402
   DotNetNuke.Entities.Portals.PortalSettings..ctor(Int32 tabId, PortalAliasInfo objPortalAliasInfo) +82
   DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +2677
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +92
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64

My other portals on this dnn installation seem to be fine.

I have a 2 day old backup to go back to, so if anyone has a suggestion for trouble shooting this one I would REALLY appreciate it.

I had that also when upgrading to 4.5.2 from 4.5.1. I ran some maintenance on the indexes and all was fine.

I am in the middle of this Index out of bounds hell and have made a few posts. I am running some live tests on a web application and my customer is onsite at a school and we keep getting these issues. I did an IIS Reset last night and the site came back up and was working. Now when I get these errors it just kicks off the participants in this test and they were able to just rebrowse the site without an IIS Reset.

The server is under pretty good CPU load between SQLServer and w3wp.exe, sometimes peaking near 100% in bursts but not constantly. I am occassionally seeing some of these in the event log, but not at the same times as the other DNN errors.

Could the SQL Server service be recycling and causing this?

Event Type: Information
Event Source: MSSQLSERVER
Event Category: (2)
Event ID: 2803
Date:  8/29/2007
Time:  7:20:37 AM
User:  N/A
Computer: DNPSERVER01
Description:
SQL Server has encountered 1 occurrence(s) of cachestore flush for the 'Bound Trees' cachestore (part of plan cache) due to some database maintenance or reconfigure operations.