Hi, I tried searching but I couldn't find anything.
I'm playing a magical character, and after a visit to the Isle of Dispair I can't cast advanced spells, the game tells me I lost my concentration. I've tried sleeping it off, moving to a different area, and purging myself of all technical items, am I missing something?

Are you casting duration-based spells along with some combat spells? There's an IN-based restriction on how many spells can be active at any given time so if you have a couple spells active before and then try to cast another, you might be going over the limit imposed by your IN stat..
From page 35 in the manual: "No caster can maintain more Spells than his Intelligence divided by 4."