IE not using some CSS or JS files, some of the time..

Question

I'm working with a client trying to solve a problem that just started on a site I built for her.  The problem started about three weeks ago.
It's a really simple ASP.NET site: http://nancyjoart.com/  One master page loads a common CSS bundle and JS bundle on all pages, however I used to have then unbundled and only bundled them to try to limit the
problem.  It didn't work, but I left the bundles as they do speed the site up.
One machine on her network constantly fails, a surface pro 2, Windows 8.1, IE11, all updates installed.  Short story:  On four pages, two public and two privately accessed, IE doesn't apply a CSS or run the javascript in the bundle.
Here are the two public pages that fail:
http://nancyjoart.com/default.aspx and
http://nancyjoart.com/gallery.aspx
If the NAV bar at the top has blue links instead of grey/black, the CSS didn't load.  If the page has no art and shows the loading GIF, or no images, the JS didn't load.
Now the fun and amazing part: the CSS that doesn't work on these four pages, is successfully used and works on every other page.
The CSS and JS files do actually get requested and downloaded by IE, as evidenced by a Network Monitor trace session and the F12 tools, but don't get applied (CSS) or loaded(JS) on these pages.
Now it gets weirder:  I can run the site fine on my Surface RT and my Pro2 from anywhere else without fail.  However, if I'm on her wifi - only half the time I can't get the scripts to run or that one CSS to apply.  I press CTRL+R and
they work fine when the page reloads, but only half the time.  In fact, it took me about a half an hour to experience the failure.  Once it happened, my dev machine would exhibit the problem, then it would work, then it would fail.
In terms of the JS - When it fails, the debugger indicates a class isn't found.  IE has parsed and downloaded that JS file, and shows the file in the debugger file list dropdown  - but doesn't seem to use it.
Even more odd, the request and responses all appear to happen quickly, all have 200 OK/Success results and the request and response headers look completely normal.  I've even saved the JS file itself and binary compared it to what I have on the server,
and it matches, so it isn't somehow getting mangled in-transit.  Even more odd than this little oddity is that once the files are requested and "fail", even if you switch to a cellular connection, the next page loads, and IE doesn't NOT load
the files correctly either.  CTRL+R eventually will get it to work on this new connection type though.
Other things I've tried:
Works on her wifi on:  iPhone, Windows Phone 8.1, Windows Phone 8, Windows Phone 7, Blackberry (Bold and Playbook) and her Windows 7 desktop.  I've put Firefox on her machine, and it works fine every time.   Anything in this list never
fails, ever except ie11 on the surfaces.
Her surface is pretty much OOB in terms of apps.  Just Modern apps installed.
My surface pro 2 dev machine is OOB too. used daily for development - Again, site works everywhere but her wifi.
Minifying the CSS or JS doesn't seem to help,
Chkdsk reports nothing,
Windows Defender is the only AV installed,
all Windows updates are installed,
Bundling the css and JS with webgrease didn't help,
I've reset the IE advanced settings, security settings, cleared the cache, tried inPrivate, tried making it trusted, nothing worked.
even reset the wifi router
She reports other websites all work fine. (** caveat: not sure how complicated these sites are, or how frequently she does this...)
Does anyone have any suggestions that they'd try next if they were in my sad shoes?
Darin R.

Answer 1

Hi,
f12>Networking tab, click the start button then refresh the page to view request/response timings.
http://nancyjoart.com/api/art/ThumbImage/fb958270-8c20-46e9-9adf-05ef6990ec85/250
Key Value
Response HTTP/1.1 200 OK
Cache-Control public, max-age=36000, s-maxage=36000
Transfer-Encoding chunked
Content-Type text/html
Server Microsoft-IIS/8.0
X-AspNet-Version 4.0.30319
X-Powered-By ASP.NET
Date Wed, 20 Aug 2014 02:34:12 GMT
you are sending back the wrong mime-type + it appears that you are not using response.close after streaming back the image in your asp.net code behind.
Open a new window in IE... copy and paste
http://nancyjoart.com/api/art/ThumbImage/fb958270-8c20-46e9-9adf-05ef6990ec85/250
in the address bar... the image loads but the document.readyState does not reach loaded. there is no EOF in the response body and it is served as text/html not image/jpg.
ensure Internet Options>Security tab, click "Reset all zones to default"... (IE has security settings for mime types) and also that Tracking Protection is turned off for the site (Tools>Tracking protection)
+ the defer attribute on the <script> tag only applies to script tags with a src attribute... validate and correct your markup errors at validator.w3.org.
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Rob^_^