This is an update of the relevant files from fireundubh's XML Fixes for game versions 2.0 and 1.35 (Steam, though there should not be any difference from retail). As such, I'll quote his description:

BEGIN QUOTE
This mod resolves XML issues with abilities and items, and as a side effect, this mod may also fix nonobvious bugs.

Types of issues resolved:

Some tags weren't properly closed.
Some comments were missing delimiters.
Some attributes were duplicated.
Some attributes were missing encapsulating spaces.

GENERAL NOTES

This mod will only ever resolve XML issues (e.g., structure, syntax, etc.)

COMPATIBILITY NOTES

This mod will conflict with any other mod that alters any of the following files:

abilities\mage.xml
items\def_item_boots.xml (1.35 only)
items\def_item_gloves.xml (1.35 only)
items\def_item_swordsilver.xml (1.35 only)
items\def_item_trophy.xml
items\def_item_witcher_sec.xml (1.35 only)
items\def_stats_item_boots.xml (1.35 only)
items\def_stats_item_pants.xml (1.35 only)

Mod authors should use these fixed XML files as the base resources for their own mods, if necessary.
END QUOTE

INSTALLATION

Extract the ZIP to the Witcher installation directory. The Steam version should be "/steam/steamapps/common/the witcher 2".

NOTICES
The files def_item_boots.xml and def_item_gloves.xml were not included because I couldn't find any syntax errors. Their structure is not beautiful but they work.

LIST OF CHANGES
mage.xml
l6: igni_speedmult= -> igni_speed mult=

def_item_swordsilver.xml
l15: enhancement_slots duplicated

def_item_trophy.xml
Multiple lines: ->

def_item_witcher_sec.xml
l816: ability_mode duplicated

def_stats_item_boots.xml
Multiple lines: display_perc duplicated

def_stats_item_pants.xml
Multiple lines: "true"mult= -> "true" mult=

THANKS
To fireundubh for bringing up the issues, to Nexus for hosting, and to CD Projekt for their hard work in bringing us excellent games.