Starting way back in Mixcraft 4.5, the Mixcraft-log.txt file is no longer located in the Acoustica Mixcraft program folder. The new location is here:
An easy way to pop up that folder is to select "All Programs" from the Windows Start menu, then choose "Acoustica Mixcraft 6" and finally "Logs."
Submit an Acoustica support request and attach your log file to help troubleshoot Mixcraft problems.
Video: How to Find Your Mixcraft Log File