Ctrl+Backspace inserts a small box instead of erasing

"Found this on an MSDN blog...

A few people in the early days of the Internet Explorer group used the Brief editor, which uses Ctrl+Backspace as the shortcut key to delete the previous word, and they liked it so much that one of them added it to the autocomplete handler. Therefore, any edit control that uses SHAutoComplete will gain this secret Ctrl+Backspace hotkey.

So it sounds like if the application does not use SHAutoComplete it will not support the feature unless it has been explicitly added by the application's author.
P.S. control-delete removes the word ahead of the cursor"