Had the same problem but, this time, I manage to use some workaround...
With mage (aloth): Just edit your grimoire and then learn the spells again (in my case they appear like..`forgotten?`...after a little while (time to the grimoire become available to use) it will be all fine;
With priest and cipher (durance and mother): You have to retrain your characters...then your last lvls spells will be available again. To retrain a char, go to any vendor, then use the button on left side of the screen..you`ll have to pay a lot of cooper and all..but...
Bugs =/