Howdy Rockers!

I've been throwing this exception on our contact us page. This page houses a User Entry form for a slightly modified version of the default External Inquiry workflow. The page in question: https://my.pinonhillschurch.com/ContactUs

Here's the exception:

An error occurred on the Pinon Hills Church site on page: 
https://my.pinonhillschurch.com:443/ContactUs

HttpException in System.Web

Message
Validation  of viewstate MAC failed. If this application is hosted by a Web Farm or  cluster, ensure that <machineKey> configuration specifies the  same validationKey and validation algorithm. AutoGenerate cannot be used  in a cluster.    See http://go.microsoft.com/fwlink/?LinkID=314055 for more information.
Stack Trace
   at System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError)
   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString, Purpose purpose)
   at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter2 formatter, String serializedState, Purpose purpose)
   at System.Web.UI.HiddenFieldPageStatePersister.Load()
   at System.Web.UI.Page.LoadPageStateFromPersistenceMedium()
   at System.Web.UI.Page.LoadAllState()
   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 ASP.themes_stark_layouts_rightsidebar_aspx.ProcessRequest(HttpContext context) in c:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\App_Web_cjsf55p1.0.cs:line 0
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

-ViewStateException in 

Message
Invalid viewstate.   	Client IP: ##.###.#.##	Port: 56544  	Referer: https://my.pinonhillschurch.com/ContactUs  	Path: /ContactUs  	User-Agent: Mozilla/5.0 (Windows NT 5.0; rv:30.1) Gecko/20100101 Firefox/30.1  	ViewState: ZMSXzavNCQbUcxIMoXcpJvAPAZYDMlbkE4qFyPjtoMgmdiwpGW437vizrwb9ZzsnaIwdDO8NAtwFt3EjxagGa6i3wppEqT7rtZWBzqeSGigrof+josXzeX8hTZ8m9RlUN97XdVgf/h2s52H0iO16Bz3lqzvVdrWlu19SFqv/3+EKv7rPH9gy4IBm67sKvu+gFr0Mmob911QFdTE6wFpz2KSLniD3LFZWtE3QZaSBWnyWPpDPqMMSU07rJzvR/Ocla2MuYyElpXkkvkeFHJp+fRG7kUQ8gAbPu1QkjQH1mup5uYJ68MGE7D9XBI3/vdbuvuFRGLhYOUePcC2ZAraudRXJa0kmBOmI0ETb8oxwce9B3tw3KGF/Ikx4hRJj7T/DUrIBkv1LEIsZzLtd3Lo5gKifboidzFDMd4IUZH1ibyJo3adTJay/rOA7Jc2kHws7s06ec4MhPvG0E93abFU2chrdoFljP1RanxDs78F2tFZsPBrDNzuv+MQCc70nHeHYCPC0g6720J28l+vL20+JDoQ0u3Rx1USoObHMLb6spMmCI3WpA67ZqB4RFJ4LP+ZZKAgZqGPtVhc5TpDF7B3QzxE7dSc9YlqhDUqS8MlTF+cqF/my/us0SGVOlU641iDpV9jshax5cIrT3A7FhCHMJ7dacWyrFhbSNZ0VJ//kWbKklzswlrc6Xfcb5PFYIorO9WMxJuoJftPYEvG5aj6w9MzUlXEBPfSsJdkgTd7+ceU9IbguM1JRZVNsDEt8RfegmJcWOq/B1oejooCXEDIOLABYaoxZOm8XAqM/rQlrz7ot/dme...
Stack Trace

First thing I checked was something related to my servers machineKey, but that had no effect that I'm aware of. The workflow does work, at least. We do get external inquires, but my big concern is we might be missing some.

We are currently running v6.10

I'm not sure what that next step to troubleshoot is, and would appreciate any feedback and advice!

Thank you!