I can no longer add/edit events.  This is vital for my site as it is a club site.  Any help would be appreciated!

Now when I try to add a new event to my calendar, I am getting an exception.  It was working ok until today.  I would appreciate any help, here is the exception info:
Error: Edit Event is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: The Runat attribute must have the value Server. ---> System.Exception: The Runat attribute must have the value Server. ---> System.Web.HttpParseException: The Runat attribute must have the value Server. ---> System.Exception: The Runat attribute must have the value Server. ---> System.Web.HttpException: The Runat attribute must have the value Server. at System.Web.UI.TemplateParser.ProcessError(String message) at System.Web.UI.TemplateParser.ProcessAttributes(Match match, ParsedAttributeCollection& attribs, Boolean fDirective, String& duplicateAttribute) at System.Web.UI.TemplateParser.ProcessBeginTag(Match match, String inputText) at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding) --- End of inner exception stack trace --- at System.Web.UI.TemplateParser.ProcessException(Exception ex) at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding) at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding) --- End of inner exception stack trace --- at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding) at System.Web.UI.TemplateParser.ParseFile(String physicalPath, VirtualPath virtualPath) at System.Web.UI.TemplateParser.ParseInternal() at System.Web.UI.TemplateParser.Parse() at System.Web.Compilation.BaseTemplateBuildProvider.get_CodeCompilerType() at System.Web.Compilation.BuildProvider.GetCompilerTypeFromBuildProvider(BuildProvider buildProvider) at System.Web.Compilation.BuildProvidersCompiler.ProcessBuildProviders() at System.Web.Compilation.BuildProvidersCompiler.PerformBuild() 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.UI.BaseTemplateParser.GetReferencedType(VirtualPath virtualPath, Boolean allowNoCompile) at System.Web.UI.BaseTemplateParser.GetUserControlType(VirtualPath virtualPath) at System.Web.UI.MainTagNameToTypeMapper.ProcessUserControlRegistration(UserControlRegisterEntry ucRegisterEntry) at System.Web.UI.BaseTemplateParser.ProcessDirective(String directiveName, IDictionary directive) at System.Web.UI.TemplateControlParser.ProcessDirective(String directiveName, IDictionary directive) at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding) --- End of inner exception stack trace --- at System.Web.UI.TemplateParser.ProcessException(Exception ex) at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding) at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding) at System.Web.UI.TemplateParser.ParseFile(String physicalPath, VirtualPath virtualPath) at System.Web.UI.TemplateParser.ParseInternal() at System.Web.UI.TemplateParser.Parse() at System.Web.Compilation.BaseTemplateBuildProvider.get_CodeCompilerType() at System.Web.Compilation.BuildProvider.GetCompilerTypeFromBuildProvider(BuildProvider buildProvider) at System.Web.Compilation.BuildProvidersCompiler.ProcessBuildProviders() at System.Web.Compilation.BuildProvidersCompiler.PerformBuild() 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.UI.TemplateControl.LoadControl(VirtualPath virtualPath) at System.Web.UI.TemplateControl.LoadControl(String virtualPath) at DotNetNuke.UI.Skins.Skin.InjectModule(Control objPane, ModuleInfo objModule, PortalSettings PortalSettings) --- End of inner exception stack trace ---

Well, that is easy to say, but it is a lot of work and takes a lot of planning to upgrade from 4.3.5 to 4.5.x.  That is not something I want to do in a rush, I could end up with the entire site down.  This site has been running and used by our club for nearly a year.  I do plan on upgrading in the not too distant future, it is not something I can rush into.  I would really appreciate some help with this exception.

Thank you for the pointer to the upgrade information, that will help when I am ready to upgrade.

Does anyone have any idea about the Runat exception is about.  I would like to get my site functional before attempting an upgrade.