This happened about a week back, I was playing as my girlfriend's mage character to get a break from my assassin for a while and to try out the magic system. We'd only recently joined the College of Winterhold and were trekking across to Dawnstar for one reason or another, blasting Horkers as we went. Blasted about 5 of them before we realised that the magic bar wasn't going down at all, whenever we cast either restoration or destruction spells. For some reason anytime we used conjuration it did, but it didn't really matter because we just double-equipped spark and went round blasting [censored] like Emperor [censored] Palpatine. Even after loading autosaves it stayed, even tried a manual save and reload and it still stayed on, so we played all evening like a suped-up mage god.

Didn't go away until we turned the ps3 off that night and tried it again the next morning. Usually I'm all into immersion, but I must admit I cried a little inside....