Download Mark Dygert mentioned solving a word puzzle when converting UV selections. I've been using this script for about 10 years. I guess it's time I shared it. :) Drag and Drop the script into your 3ds Max viewport and look in the monsterBlues category to bind to a hotkey or quad menu.
Bumping this old topic because I added your script to one of mine which lets you do the same type of selection conversions despite which mode you're in (Editable Poly / Edit Poly / UV) with a single key for each component type. https://dl.dropboxusercontent.com/u/4210886/g_convertComponent.mcr