Apple is now seeding a third developer preview of OS X Mountain Lion. The new build is listed as 12A178q, as opposed to the previous one's 12A154q. The OS is still saddled with a number of known issues, including several related to FileVault. Canceling the preview installer's restart, for instance, may prevent people from entering a password until Disk Utility is used to unlock and repair a volume; some installations on top of OS X 10.7.2 may fail if the older OS has FileVault enabled. FileVault accounts created before Lion won't work at all at in the current Mount
