Unable to get in MSN till I use System Restore

OK this happened the other day ..I tried to log into MSN
and got the message they were either having probs with
their server or it was my internet connection...so I
decided to just use Internet Explorer and it worked fine
till I tried to go to hotmail..thought ok MSN is all
messed up, but then I went ahead and tried to log onto
another site which requires my username and password (it
wasn't MSN related) well the page came up as unavaiable,
then I started thinking it wasn't MSN it was my
computer..so I did a system restore and presto all is
back to normal..I could log into where ever I wanted. Now
this morning the same thing happened and I did another
system restore, and again it was back to normal. My
question is...Does anyone have any clue as to WHY this is
happening? Will it happen again? Can I prevent it?
Please HELP! Thanks in advance...Jessi