If you're still running 6.4.0, upgrade to 6.4.1 (May have to do it manually - download the 6.4.1 zip file from limetech's website, and extra all the bz* files from it and overwrite the ones on the flash drive)
There was a bug in 6.4.0 that caused this. After 6.4.1 is up, you'll still have to make a change in VM Settings.