Users have reported issues where they cannot send songs from FrostWire to their iTunes after having updated iTunes to version 10.6.3.25 (latest today)

Here's a few things you can do:

DELETING AND RECREATING THE FROSTWIRE PLAYLIST.
1. Go to iTunes.
2. Delete the "FrostWire" playlist.
3. Go back to FrostWire, select the files you want to send to iTunes, right click on them and select "Send to iTunes"

iTunes should create the FrostWire playlist.

SENDING FROSTWIRE PLAYLISTS TO ITUNES.
1. Create a playlist with the files you want to send inside FrostWire.
2. Right click on the playlist name (on the left hand side of the Librar) > Export Playlist to iTunes

Or you can revert back to an older iTunes version, should work perfectly fine

Cheers. (We'll be working on fixing this small incompatibility, hopefully iTunes hasn't closed itself completely from drag n drop)