I encountered same issue "Login/Register Popup" with DNN 6.2.0.
From Chris's advise, it worked on my localhost by modified following part:
1.admin\Skins\Login.ascx.cs (popup login)
//loginLink.NavigateUrl = Globals.LoginURL(returnUrl, (Request.QueryString["override"] != null));
//enhancedLoginLink.NavigateUrl = loginLink.NavigateUrl;
var url = Globals.LoginURL(returnUrl, (Request.QueryString["override"] != null));
loginLink.NavigateUrl = (PortalSettings.EnablePopUps && PortalSettings.LoginTabId == Null.NullInteger) ? UrlUtils.PopUpUrl(url, this, PortalSettings, false, false, 300, 650) : url;
enhancedLoginLink.NavigateUrl = loginLink.NavigateUrl;
2.admin\Skins\User.ascx.cs (popup register)
//registerLink.NavigateUrl = !String.IsNullOrEmpty(URL)
// ? URL
// : Globals.RegisterURL(HttpUtility.UrlEncode(Globals.NavigateURL()), Null.NullString);
//enhancedRegisterLink.NavigateUrl = registerLink.NavigateUrl;
var url = !String.IsNullOrEmpty(URL) ? URL : Globals.RegisterURL(HttpUtility.UrlEncode(Globals.NavigateURL()), Null.NullString);
registerLink.NavigateUrl = PortalSettings.EnablePopUps && PortalSettings.LoginTabId == Null.NullInteger ? UrlUtils.PopUpUrl(url, this, PortalSettings, false, false, 600, 950) : url;
enhancedRegisterLink.NavigateUrl = registerLink.NavigateUrl;
It compiled successfully and worked well in my local machine.
I also want it works as well on my hosting server.
I tried to copy *.dll files under bin folder to web hosting server, but it doesn't work.
Any body knows how to let the hosting server works (popup login) as my localhost?
Thanks in advance.