InvokePattern.Invoke throwing Win32Exception "Hot key is already registered"

Hello, 

I am currently using the UIAutomation API to handle Javascript dialogs.  For the most part this has worked great but every so often I get this random Exception and I'm not sure how to work around/fix it.

Exception:Hot key is already registered

Type:System.ComponentModel.Win32Exception

Stack:   at MS.Internal.AutomationProxies.Misc.ThrowWin32ExceptionsIfError(Int32 errorCode)

   at MS.Internal.AutomationProxies.Misc.SetFocus(IntPtr hwnd)

   at MS.Internal.AutomationProxies.WindowsButton.Invoke()

   at MS.Internal.AutomationProxies.WindowsButton.System.Windows.Automation.Provider.IInvokeProvider.Invoke()

   at System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32 errorCode, IntPtr errorInfo)

   at System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(Int32 errorCode)

   at MS.Internal.Automation.UiaCoreApi.CheckError(Int32 hr)

   at System.Windows.Automation.InvokePattern.Invoke()

This is the code that I am using to handle the dialog.

var okButton = window.FindFirst(TreeScope.Descendants, new PropertyCondition(AutomationElement.AutomationIdProperty, "1"));var invokePattern = okButton.GetCurrentPattern(InvokePattern.Pattern) as InvokePattern;

invokePattern.Invoke();

This exception doesn't always happen but if I run ~100 scripts that use it I find it happens about 20 times.

I'm running these Scripts using the Microsoft Test Manager and the Microsoft Test Agents on Windows 7 and Windows Server 2008 boxes.

Any help would be appreciated. 

Thanks