Thank you -- I had the same problem, and removing ufsd.fs solved it. This is a Paragon universal file system driver, but it should be removed from Lion. After removing it I installed Paragon 9.0 and it all works!To read/write NTFS on Lion I had to delete the folder 'ufsd.fs' from /system/Library/filesystem
I installed a third party NTFS driver (Paragon 9.0.1 worked for me)
Now my NTFS drive mounts and I can read/write.
Hope that helps.