It's not a fix, sadly, but a work-around (as I said). Workaholic just means that my sim can work from home in her own time to make up for the time when the game says that she is 'going to work' in the career tab, when she is actually at work, working hard, and all the smilies are bright green big smilies. I haven't pin-pointed if it's specific times of specific careers, because sofar it appears to be on random days, and even when the boss is at work too (although midnight seems to be when performance picks up again in Criminal). There is also a glitch that career performance will drop on a Wednesday, even though the sim can't work. I haven't played other careers since updating, other than criminal and culinary. It has happend in both.
That is only, however, if it will be allowed. It definitely is a glitch. There is a thread on here somewhere about it, and a mention about the Wednesday thing on the wiki.