Just re-downloaded and installed the fix, same problem. 

Getting error message when trying to open the image gallery from within the editor.

AssemblyVersion: 04.03.05
PortalID: 0
PortalName: portal name
UserID: 241
UserName: domain\username
ActiveTabID: 36
ActiveTabName: Home
RawURL: /Providers/HtmlEditorProviders/Ftb3HtmlEditorProvider/ftb3/ftb.imagegallery.aspx?cif=~/Portals/0/&rif=~/Portals/0/&portalid=0&ftb=dnn_ctr1531_EditHTML_teContent_teContent
AbsoluteURL: /Providers/HtmlEditorProviders/Ftb3HtmlEditorProvider/ftb3/ftb.imagegallery.aspx
AbsoluteURLReferrer:
UserAgent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; MAPSIE; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.1; MAPSIE; MAPSIE)
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: f9aa7ba6-2bc5-481f-8289-5d122186244f
InnerException: Unhandled Error:
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: System.Web.Compilation.BuildManager.CompileWebFile
StackTrace:
Message: System.Exception: Unhandled Error: ---> System.Web.HttpCompileException: C:\DNN\Providers\HtmlEditorProviders\Ftb3HtmlEditorProvider\ftb3\ftb.imagegallery.aspx(1): error BC30456: 'InitializeCulture' is not a member of 'ASP.providers_htmleditorproviders_ftb3htmleditorprovider_ftb3_ftb_imagegallery_aspx'. at System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath) at System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile) at System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile) at System.Web.Compilation.BuildManager.GetVirtualPathObjectFactory(VirtualPath virtualPath, HttpContext context, Boolean allowCrossApp, Boolean noAssert) at System.Web.Compilation.BuildManager.CreateInstanceFromVirtualPath(VirtualPath virtualPath, Type requiredBaseType, HttpContext context, Boolean allowCrossApp, Boolean noAssert) at System.Web.UI.PageHandlerFactory.GetHandlerHelper(HttpContext context, String requestType, VirtualPath virtualPath, String physicalPath) at System.Web.UI.PageHandlerFactory.System.Web.IHttpHandlerFactory2.GetHandler(HttpContext context, String requestType, VirtualPath virtualPath, String physicalPath) at System.Web.HttpApplication.MapHttpHandler(HttpContext context, String requestType, VirtualPath path, String pathTranslated, Boolean useAppConfig) at System.Web.HttpApplication.MapHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) --- End of inner exception stack trace ---
Source:
Server Name: WEBSERVER

Did an IISRESET, but will try rebooting the server later...

Yeah I tried to duplicate it myself this morning and couldn't. I'm going to revisit the problem this afternoon to see if I can't figure out why it's blowing up the FTB.

Dan, do you have a test install of DNN4 somewhere that you can use for testing? I'd like a second opinion before I say it's fixed again.