When you launch Emotion, Windows shows a "Please wait while Windows configures Emotionx64" and a "Error 1310 Writing to file", and Emotion does not start.
This usually happens when an antivirus blocks the access to a file, because it suspects it could potentially harm your computer.
Obviously no file required to use Emotion or MERGING+NADAC will harm your computer! That is a "false positive".
Nowadays antivirus updates their databases very often, up to several times a day for some.
So even if Emotion was working the day before, it could be affected by this issue today.