When Firefox 2.0 came out, I upgraded my MacBook immediately . Almost as immediately , Firefox proceeded to crash and I downgraded. Today, I tried to upgrade again. Every time I downloaded the Firefox dmg , it was corrupt and refused to mount. Using the disk utility, I turned on journalling (see previous post), repaired permissions (I still think this is an odd operation), and I verified the disk. Still, I kept downloading a corrupt Firefox image. So, finally I decided to blame FileVault . I disabled it (that took about half-an-hour), downloaded Firefox 2.0, and successfully installed it. Now I'm waiting for FileVault to turn on again. Moral of the story: If you're experiencing problems with corrupted data, turn off FileFault FileVault .