that's strange. following the guide in the sticky'd thread, my game looks like this: http://zeckul.files.wordpress.com/2012/01/011012_2203_icewinddale13.png?w=584
is the widescreen mod you're using the one up at http://www.gibberlings3.net/widescreen
I'm not using the widescreen mod. Just run the config utility from the main IWD2 folder. Under the Graphics tab, Just check the Unsupported box in the Resolution field. Depends on the res you want. The games natively supports 800x600, 1024x768, 1280x960, 1600x1200, and 2048x1536 resolutions
If you're looking for s different resolution, then you'll need to use the widescreen mod, and unfortunately, that does not scale the UI. Check This Installation Guide
for more info (it talks about the Widescreen mod at the bottom).