I have all of the patches loaded and currently have an 8th level party which includes a cleric of Pelor. Oddly enough, he hasn't gained access to 3rd level spells or above. Ironically, he has available slots for 3rd level spells, although I'm forced to place 1st or 2nd level spells in those slots. ??? The DND PHB states that a cleric can lose his abilities if he does "bad things", but he can atone for those crimes. Of course, there's no mention of this in the TOEE game manual, and there's no atonement spell either. Is this some malevolent bug?
Only paladins can be fallen in toee, what is your clerics wisdom score? It needs to be 10 plus the level of the spell (you'd need a 13 for 3rd level spells).
Have you patched the game, shareware? I remember there were some problems with clerics not getting their spells correctly in the original version of the game.
