Cast on block Crash to Desktop

I have just tried swapping over to a Svalinn Crucible Tower Shield and anytime I try to add to the Cast on block skill sockets I Crash to Desktop.
Below are the Copy - Paste of the item in use.

Item Class: Shields
Rarity: Unique
Svalinn
Crucible Tower Shield
--------
Block chance: 26%
Armour: 265 (augmented)
--------
Requires: Level 78, 83 Str
--------
Sockets: S
--------
Item Level: 83
--------
Grants Skill: Raise Shield
Grants Skill: Cast on Block
--------
141% increased Armour
-13% to maximum Block chance
Block chance is Lucky
--------
The priests found the Great Shield the night it fell to Middengard,
but it was the smiths who delved into the secrets it held.

+
same thing