Hi Dimitar,
This was one of the first things I tried, but it does not help. Looks like you add the 'Loading...' after OnClientItemsRequesting.
I used the code posted by Chris where he checks for html().length and this works better, as html is empty on initial load only.
Now, it appears that I have some columns where a.html() is null. For these columns the prepend() does not work. So again, there is no Loading... indicator when the combobox first opens (work normally for subsequent requests).
Do you have another workaround for this problem (internally you must be doing something different since it works regardless of a.html())?
Do you have an idea what might cause a.html() to be null?