[23/3/2015 19:35:26 PM] [Client thread/INFO] [STDERR]: [tombenpotter.sanguimancy.registry.PotionsRegistry:potionPreInit:31]: Severe error during potions pre-init, please report this to the mod author:
[23/3/2015 19:35:26 PM] [19:35:26] [Client thread/INFO] [STDERR]: [tombenpotter.sanguimancy.registry.PotionsRegistry:potionPreInit:32]: java.lang.ArrayIndexOutOfBoundsException

forge 1291 , mod version pre24

I don't get this error. Could you post your full log file (via pastebin or something) so we can see which mods you have installed?

That just means he changed one of the potion Ids in the config, but with a value that was too big. Not a bug

Changing the potion id's to 127 or under still gives this error. Pretty sure that is a bug.
Also some mods now extend the potion array allowing for using potion id of over 127.
So might want to look into allowing it/fixing it so that you can set it to above what used to be the maximum value.