I have noticed that spells higher than 3rd level can't seem to be dispelled (at least those that use the standard dispel handler). So spells like improved invisibility, fire shield, freedom of movement and similar spells can't be dispelled. Dispel magic doesn't seem to notice those spells at all. I think I have a fix for this to add to temple+. I was wondering if someone would independently verify this issue with their game. Thanks!