After upgrading my Mac from OS X 10.6.8 Snow Leopard to OS X 10.7.3 Lion, I discovered I could no longer write files to external NTFS-formatted drives. The problem is MacFUSE which, I found out, does not support the new 64-bit kernel. If this is happening to you, you must remove the old MacFUSE and install the newer version, which does support the 64-bit kernel. Here's how.
Next, download MacFuse from Tuxera. Version 2.2 is 64-bit compatible and can be found here
. If you haven't installed NTFS-3G, download this
. The Oct. 11, 2010 version is the most current, working binary. Again, double click the install NTFS-3G package and follow the instructions. When prompted to choose No caching or UBLIO caching, I recommend UBLIO. The performance boost is worth the very minor risk. And if you're paranoid, just make sure to copy your files to the external drive, not move them.