Just a thought but some ppl may come across this again in the furture, most ppl are using the trialedition of MSSQL, if one day it decides not to connect like in the 1st post, it maybe because the trial ran out. Simple fix is go treat yourself to a full version either by buying it or good old trust worthy torrents.
Hope this is of some help to someone as this stumped me at first when it happened to me >.< lol