MDSNResponder no such file or directory

had a bit of a scare over the past 24 hours.  my laptop wasn't starting up.  i'd turn it on and the grey screen would come up with the apple logo and that was it, even after 45 minutes.  now i didn't sit in front of my laptop for 45 minutes watching the grey screen.  i was doing a bit of research at this time figuring out how to fix this problem.  after plowing through the support forums on apple.com i tried various things.  about a week ago i had installed some memory so maybe perhaps that was causing the problem.  so i removed the newly installed memory and turned on the laptop but it was not booting up.  that wasn't causing the problem so i put the memory back in.  i tried resetting the system management controller but that didn't work.  i tried resetting the NVRAM but again, that didn't do anything.  running the laptop through the disk utility on the home computer didn't do anything either.  at this point i decided to give up for the night because bethany was over and i know she didn't want to watch me try and fix my laptop all night.

so here we are today, woke up and went right back at trying to figure out what's wrong with my laptop.  i booted it up in verbose mode, which shows what it's doing when it's starting up, like this:

everything was looking fine until it showed a couple errors and kept repeating every 5 seconds

MDSNResponder no such file or directory

MDSNResponder no such file or directory

MDSNResponder no such file or directory

so i typed that into google and found a forum where someone was having the same problem and 

figured out how to fix it. it was an error with the file sharing on the hard drive. I must have 

accidently changed one of the settings from "read and write" to "read only" and that was causing 

the start up to freeze. the person on the forum explained how he fixed his problem while in single 

user mode, which is like verbose mode but you can input commands. his way of doing it was a bit

too confusing to me but i came up with a much easier way of fixing the problem. i turned my laptop

on in target disk mode, which basically turns the laptop into an external hard drive, and plugged it

into the home computer. i pulled up the info window for the laptop hard drive and sure enough, one

of the settings was set to "read only":

i simply reset it to "read & write," ejected the laptop from the computer, turned it off and turned it back on and sure 'nuff, it started up just fine.  this made me pretty darn happy because i was beginning to worry that i was going to need a new laptop.  i was beginning to think that maybe the hard drive died or it was a problem with the logic board or something major like that.  luckly this was not the case!