Thanks for the additional info. I don't think using .ashx as extension has any effect here and I doubt that me using html and you using aspx would make any difference, but still, you never know. The different and non-recommended DOCTYPE I placed in the Html files were placed there for a purpose and I was hoping you would modify the application and upload it so I could reproduce.
I do however think that you and James have both hit the nail directly on the head here (thanks James) and the reason for me not seeing anything wrong was because of my IE9 jumped into Compatibility mode for whatever reason. As you mention yourself, turning on IE compatibility mode makes the Visual WebGui application work correctly. When making sure IE9 is not in compatibility mode, I can see the problem (finally).
Googling a bit on this problem, it seems that it is an IE(9) problem with IFrames, where IE9 forces the child IFrames to have the same doctype as the parent. You can see this thread here for instance. Acting on the recommended, or more precisely the only, workaround available for us generally I placed the following meta in the head section of the Html file (see description below):
<meta http-equiv="X-UA-Compatible" content="IE=8" />
Ok, if you look at the sample applcation (the v2 one I uploaded) and run it (loading HtmlPage1.htm at startup) unchanged and make sure IE9 is not in compabitility mode, you should see the problem... meaning the Menues will popup/dropdown blank. Remember that HtmlPage1 loads HtmlPage2 in an IFrame which loads Form1.wgx in an IFrame.
If you place the above meta inside HtmlPage1.htm, the Form1 works (tested on 6.4.0 Release Beta3 JQT and also on upcoming WinWeb 6.4.0 Release e).
If you place the above meta only inside HtmlPage2.htm and not in HtmlPage1.htm, it doesn't work.
Please check if you can use this information to modify your Html (aspx) pages to include this meta tag and see if you can work around the problem that way. It doesn't seem that we have a whole lot of options for IE9 at the moment.
P.S. In association with our upcoming Enterprize Mobile framework (due end of Q2) a new DOCTYPE will be introduced in Visual WebGui application. Could be that it will fix this incompatibility with IE9 and IFrames, I just can't fully confirm yet.
Hope this helps,