Hi Kevin, I am having the same issue since I upgraded to windows 8.1.
I was happily powering a Catleap Q271 monitor at 2560x1440 over both HDMI and VGA from my Samsung Chronos 7 Laptop with Intel HD4000 gfx + dedicated 8870M radeon Card. I believe it's the HD4000 that is outputting video to the ports?
I had created my custom resolutions in the "Intel Graphics and Media Control Panel" program. This program seems to have been uninstalled during the Win 8.1 upgrade (windows thinks the program is installed but the exe is missing). I am unable to select a custom resolution in the "Intel(R) HD graphics" program.
I used the following settings: http://www.notebookcheck.net/fileadmin/_migrated/pics/2560x1440_intel_hd_graphics_4000_ivy_bridge.png
I installed Win8.1 tonight and the best it can muster is 1920x1200 over HDMI (i still get 2560x1440 over VGA but it does not look as sharp as I was getting over HDMI)
Please can you talk to your engineers about this since I was viewing my display at 2560x1440, and in fact i was able to run both the VGA and HDMI at the same time from this laptop and both were 2560x1440.
See the enclosed screenshot of VGA set to 2560x1440:
So, as you can see from both image links in this post, people are getting 2560x1440 from these cards over HDMI and VGA, despite what the official specs are saying.