embedded firefox - exception with default engine (RDM x64)

hi!
when i launch an embedded firefox with engine "default" in RDM 10.0.4.0 64-BIT i get the following exception.

it works when i change the engine to "MozNET (R 19.8)" though.

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See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
at Skybound.Gecko.GeckoWebBrowser.Navigate(String url, GeckoLoadFlags loadFlags, String referrer, Byte[] postData, String additionalHeaders)
at Skybound.Gecko.GeckoWebBrowser.Navigate(String url)
at Devolutions.RemoteDesktopManager.Frames.Embedded.FreEmbeddedFirefoxGeckoBrowserPage.timer_Tick(Object sender, EventArgs e)
at System.Windows.Forms.Timer.OnTick(EventArgs e)
at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)


************** Loaded Assemblies **************
mscorlib
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.34014 built by: FX45W81RTMGDR
CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/mscorlib.dll
----------------------------------------
Embedded32
Assembly Version: 10.0.4.0
Win32 Version: 10.0.4.0
CodeBase: file:///C:/RDM/Embedded32.exe
----------------------------------------
System.Windows.Forms
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.33440 built by: FX45W81RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Windows.Forms/v4.0_4.0.0.0__b77a5c561934e089/System.Windows.Forms.dll
----------------------------------------
System.Drawing
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.33440 built by: FX45W81RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Drawing/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll
----------------------------------------
System
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.34239 built by: FX452RTMGDR
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System/v4.0_4.0.0.0__b77a5c561934e089/System.dll
----------------------------------------
zip
Assembly Version: 0.0.0.0
Win32 Version: 10.0.4.0
CodeBase: file:///C:/RDM/Embedded32.exe
----------------------------------------
Embedded32
Assembly Version: 10.0.4.0
Win32 Version: 10.0.4.0
CodeBase: file:///C:/RDM/Embedded32.exe
----------------------------------------
Devolutions.Utils
Assembly Version: 3.0.0.0
Win32 Version: 3.0.0.0
CodeBase: file:///C:/RDM/Devolutions.Utils.DLL
----------------------------------------
System.Core
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.33440 built by: FX45W81RTMREL
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Core/v4.0_4.0.0.0__b77a5c561934e089/System.Core.dll
----------------------------------------
DevExpress.XtraEditors.v14.1
Assembly Version: 14.1.5.0
Win32 Version: 14.1.5.0
CodeBase: file:///C:/RDM/DevExpress.XtraEditors.v14.1.DLL
----------------------------------------
DevExpress.Utils.v14.1
Assembly Version: 14.1.5.0
Win32 Version: 14.1.5.0
CodeBase: file:///C:/RDM/DevExpress.Utils.v14.1.DLL
----------------------------------------
DevExpress.Data.v14.1
Assembly Version: 14.1.5.0
Win32 Version: 14.1.5.0
CodeBase: file:///C:/RDM/DevExpress.Data.v14.1.DLL
----------------------------------------
System.Xml
Assembly Version: 4.0.0.0
Win32 Version: 4.0.30319.34230 built by: FX452RTMGDR
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Xml/v4.0_4.0.0.0__b77a5c561934e089/System.Xml.dll
----------------------------------------

************** JIT Debugging **************
To enable just-in-time (JIT) debugging, the .config file for this
application or computer (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.

For example:

<configuration>
<system.windows.forms jitDebugging="true" />
</configuration>

When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the computer
rather than be handled by this dialog box.

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