OMA Event ID 1503 problem

I am running SBS2003 standard and have OWA running well. However, when I try to access http://server/oma, I get the error message "A System error has occurred while processing your request. Please try again. If the problem persists, contact your administrator." The error logged in the Event logs is Event ID 1503. I have read up on most of the other 1503, but have not come across one with the following text:

An unknown error occurred while processing the current request:
Message: Index was out of range.  Must be non-negative and less than the size of the collection.
Parameter name: startIndex
Source: mscorlib
Stack trace:
   at System.Globalization.CompareInfo.IndexOfString(Void* pSortingTable, Int32 win32LCID, String source, String value, Int32 startIndex, Int32 count, Int32 options)
   at System.Globalization.CompareInfo.IndexOf(String source, String value, Int32 startIndex)
   at Microsoft.Exchange.OMA.Preferencing.AdUserObject.get_globalWirelessEnable()
   at Microsoft.Exchange.OMA.Preferencing.AdUserObject.get_UserIsWirelesslyEnabled()
   at Microsoft.Exchange.OMA.Preferencing.OmaUserInfo.get_UserIsWirelesslyEnabled()
   at Microsoft.Exchange.OMA.UserInterface.Global.Session_Start(Object sender, EventArgs e)

Message: Exception of type Microsoft.Exchange.OMA.DataProviderInterface.ProviderException was thrown.
EventMessage:
UserMessage: A System error has occurred while processing your request. Please try again. If the problem persists, contact your administrator.
Source: Microsoft.Exchange.OMA.UserInterface
Stack trace:
   at Microsoft.Exchange.OMA.UserInterface.Global.Session_Start(Object sender, EventArgs e)
   at System.Web.SessionState.SessionStateModule.RaiseOnStart(EventArgs e)
   at System.Web.SessionState.SessionStateModule.CompleteAcquireState()
   at System.Web.SessionState.SessionStateModule.BeginAcquireState(Object source, EventArgs e, AsyncCallback cb, Object extraData)
   at System.Web.AsyncEventExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

So far, I have tried the following:
1. Followed settings for http://support.microsoft.com/?id=898131
2. Had a look at http://support.microsoft.com/default.aspx?scid=kb;en-us;817379
3. Looked at http://support.microsoft.com/default.aspx?scid=kb;en-us;842119

Thw wierd thing is that I have set up several other servers, and oma is working fine on the other servers. However, this one hosts a few websites.

Any help would be greatly appreciated. Full points will be awarded. I've been messing around with this for over 2 months off and on.