Exception after choosing region/language in Exchange 2013 OWA

Okay, so, I've looked everywhere and I have had no luck at all.

Whenever I try to log in, using OWA, to any mailbox it asks me to select my language and region/timezone. After accepting these changes, I'm brought to the standard Exchange "oops something went wrong error", but I can proceed to the mailbox if I just refresh the page.  This happens every time and my language settings are not saved at all.

Before the cumulative update, it actually displayed the standard ASP.NET exception page, but with the update it just displays a generic error.

Here is the exception/stack trace as logged in the Event Log:

Event code: 3005 
Event message: An unhandled exception has occurred. 
Event time: 5/16/2013 11:20:04 PM 
Event time (UTC): 5/17/2013 6:20:04 AM 
Event ID: a722cf635ace4e55a26c355d3882f120 
Event sequence: 18 
Event occurrence: 1 
Event detail code: 0 
Application information: 
    Application domain: /LM/W3SVC/2/ROOT/owa-1-130132451308249489 
    Trust level: Full 
    Application Virtual Path: /owa 
    Application Path: C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\owa\ 
    Machine name: EX10 
Process information: 
    Process ID: 15516 
    Process name: w3wp.exe 
    Account name: NT AUTHORITY\SYSTEM 
Exception information: 
    Exception type: NullReferenceException 
    Exception message: Object reference not set to an instance of an object.
   at Microsoft.Exchange.Clients.Owa.Core.Culture.IsThreadCultureSet(OwaContext owaContext)
   at Microsoft.Exchange.Clients.Owa.Core.Culture.SetThreadCulture(OwaContext owaContext)
   at Microsoft.Exchange.Clients.Owa.Core.Utilities.HandleException(OwaContext owaContext, Exception exception, Boolean showErrorInPage)
   at Microsoft.Exchange.Clients.Owa.Core.OwaPage.OnError(EventArgs e)
   at System.Web.UI.Page.HandleError(Exception e)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest()
   at System.Web.UI.Page.ProcessRequest(HttpContext context)
   at Microsoft.Exchange.Clients.Owa.Core.OwaPage.ProcessRequest(HttpContext context)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

 
 
Request information: 
    Request URL: https://xxxx:444/owa/info.aspx?Msg=1 
    Request path: /owa/info.aspx 
    User host address: 10.1.1.11 
    User: DOMAIN\daniel00000 
    Is authenticated: True 
    Authentication Type: Basic 
    Thread account name: NT AUTHORITY\SYSTEM 
 
Thread information: 
    Thread ID: 49 
    Thread account name: NT AUTHORITY\SYSTEM 
    Is impersonating: False 
    Stack trace:    at Microsoft.Exchange.Clients.Owa.Core.Culture.IsThreadCultureSet(OwaContext owaContext)
   at Microsoft.Exchange.Clients.Owa.Core.Culture.SetThreadCulture(OwaContext owaContext)
   at Microsoft.Exchange.Clients.Owa.Core.Utilities.HandleException(OwaContext owaContext, Exception exception, Boolean showErrorInPage)
   at Microsoft.Exchange.Clients.Owa.Core.OwaPage.OnError(EventArgs e)
   at System.Web.UI.Page.HandleError(Exception e)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest()
   at System.Web.UI.Page.ProcessRequest(HttpContext context)
   at Microsoft.Exchange.Clients.Owa.Core.OwaPage.ProcessRequest(HttpContext context)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
Custom event details: 

Any help with this issue is appreciated. While OWA still functions fine if I ignore the error, I think we can all agree that's not an acceptable solution, especially considering that my timezone and language selection aren't saving either.

Thanks in advance!