UNSOUND  I don't really understand what this has to do with NTFS-3G. You can't install NTFS-3G on an Airport Extreme, and the problematic hard disk is formatted as HFS+, isn't it?

Just because two things happen in sequence doesn't mean that they are related. NTFS-3G can not in any way affect what happens on your Airport Extreme, and it doesn't touch non-NTFS file systems.

It seems that you should contact Apple about file system corruption when using Airport Extreme.  
(Version 2009.4.4)

MARSOFEARTH  It is difficult to say that NTFS-3G caused the file structure problem but rather after installation called a "Search" for drives connected to your Mac and in doing so your drive was found faulty.

The good news is that it is likely a "fairly" simple fix.

There is the free way or the "Paid" way. TechTool Pro and DiskWarrior are two very capable tools and in my opinion well worth the price to have on hand.

The other way is to use FSCK which is freely available in your Mac OS X UNIX underpinnings. However if you have never used a Terminal command this can be a bit overwhelming for some.

http://www.osxfaq.com/Tutorials/fsck/index.ws is a good resource if you wish to learn how to use these free tools in Mac OS X.

http://www.macosxhints.com is another fine community resource filled with knowledgeable people.

NOTE: IF after fixing the file structure on your Drive, you find the problem happening again, you will want to find out if it is something within your connection or use that is causing the problem or perhaps there is a "Bad Sector" on your drive, OR in a worse case scenario a sign that your disk is beginning to fail.   
(Version 2009.4.4)

MARSOFEARTH  It is difficult to say that NTFS-3G caused the file structure problem but rather after installation called a "Search" for drives connected to your Mac and in doing so your drive was found faulty.

The good news is that it is likely a "fairly" simple fix.

There is the free way or the "Paid" way. TechTool Pro and DiskWarrior are two very capable tools and in my opinion well worth the price to have on hand.

The other way is to use FSCK which is freely available in your Mac OS X UNIX underpinnings. However if you have never used a Terminal command this can be a bit overwhelming for some.

http://www.osxfaq.com/Tutorials/fsck/index.ws is a good resource if you wish to learn how to use these free tools in Mac OS X.

http://www.macosxhints.com is another fine community resource filled with knowledgeable people.

NOTE: IF after fixing the file structure on your Drive, you find the problem happening again, you will want to find out if it is something within your connection or use that is causing the problem or perhaps there is a "Bad Sector" on your drive, OR in a worse case scenario a sign that your disk is beginning to fail.   
(Version 2009.4.4)