Self Mods that add stats now have a chance to fail like Item Mods do, except that instead of "ruining" your body, it will just reset your stats back down to 100 (+1 extra for every level you have gained.) This might actually make some people happy because then they could distribute their points again better. This change is to stop people from massing tons of selfmods on yourself... because every time you use a new one, you are basically "betting" the ones you have already done, and eventually the odds will make it so you lose. Its good to be a little buff, but not uber uber buff. =)
ADDITIONALLY, new instructions have been added to all Mod scrolls. DO NOT use ANY sort of mod scroll if the thing you are using it on has a spell effecting its stats.
SO, if you are using a selfmod scroll, WAIT until all your enchantments on yourself and on your items have expired.
If you are using an itemmod scroll, you just have to wait until the enchantments on that particular item expire.
If you ignore this warning and screw your stats or item up, it will not be fixed by admin... you will have to go purchase a stat reset scroll or buy a new item to replace the one that got destroyed.