Not getting DropDownList value when setting it via JavaScript

So today I had a problem which was doing my head in. I had a form which has a bunch of DropDownLists on it, some of which are disabled (depending on the radio button selection). Regardless of whether the DropDownList was available I needed to read the value (which was often set via JavaScript) back on the server. But I noticed that the value I was setting via JavaScript wasn’t making it way back to the server if I read the dropDownList.