Missing sim

[poss714]

I am really disappointed at the moment with Sims 3.  I have most of the games just a couple of "Stuff" discs not yet purchased and like I said earlier I am disappointed in the glitches with Sims 3.  I have a number of Error 12 messages, the game seems to slow right down for awhile, then comes good for a bit then goes slow again (yes my computer is fine and I have all the requirements).  Now one of my Sims has just disappeared and I can't get her back.  Her daughter has "Mum" in her relationship panel, but mum is greyed out.  Where did she go?  She didn't die, move out or go on holiday.  I also find that if it is snowing then the game won't save.  Am I doing something wrong?  Please help I really love Sims and would prefer not to have to go back to Sims 2 if I can help it.  Thanks in advance.

[EA_Spectre]

Have you already tried everything that is mentioned here for error 12?

Save Errors (Error 12, 13, 15, 16) - by crinrict

While saving I get the error message: "Error 12 (or 13 or 15 or 16). Please see Read-Me for more information".