I don't remember if the Launcher integrity checks itself, but I would try downloading and installing it in another directory (or copying the downloaded one into your new directory) to rule out a corrupt launcher.
Outside of that, the things to check are:
-Does it happen without MQ2 loaded?
-Antivirus (possible you excluded MQ2, but not your EQ directory and your AV is stopping the launcher from launching EQ with MQ2)
-chkdsk /r (possible you have a disk issue)