I normally start the day with a group Protection from Evil, Stoneskins and Ironskins for those that have them, Chaotic Commands and negative plane Protection in the Underdark... and maybe resist fear, fire, cold and a few more. I also have lots of protection rings and cloaks and boots, etc. Then I read that casting Magic Resistance on Frikraag actually hurts instead of helping him. Now I'm concerned.

Are Cleric and Mage spells cumulative or are there combos which are synergistic and, of greater concern, some which are counteractive?

that's a good question and i hope someone comes up with a good answer
because i would like to know this too !!!
if i were you though i shouldn't worry too much,the way you protect
yourself you'll probably survive a nucleair holocaust(lol)

Actually, Beholders get to me pretty quick. I hide and use elementals. You see, I was in a hurry to get to Imoen so I took the portal instead of the ship to the Underdark - Now all I can do is 'reflect' upon my mistake. http://www.ironworksforum.com/ubb/no...ons/icon31.gif

Well, the only protection spell i know that canciles out others is the 1st level mage spell reflect Image, it canciles out mirror image simularicun and even project image.

Hope this answers your question ;)

magic resistance does fix the subject's magic resistance at a certain percentage.. at 2% per priest level to be precise. so it can lower resistance too.. if thats your question. and yes.. it does have the same effect on firkraag.. i cast magic resistance and lower resistance upon him paralelly using jaheira & self, that exposed him to lottsa azzwhipping from things like abi-dalzim's and such.
but why are you concerned? none of the protections you mentioned should be cancelled by magic resistance.

now along the same lines i have a question:
i'm real confused with the various spell protections available. its like this.. i'm a mage and cast spell trap upon myself at a certain point in the game (using the staff of the magi). this i followed up with a spell shield (in case some mean guy cancels my precious spell trap with a stupid piercing spell). the problem is i dont think the spell shield worked.. i mean it seemed to be absorbed by the spell trap. does anyone know if this is true?
do my own spell protections interact with one another? if so.. thats very annoying. anyone researched this a bit?