Torrent Info Order Bad
Torrent files contain metadata describing the download's content. In particular they contain an 'info' section that is used to derive a unique hash that identifies the torrent (the hash itself is not explicitly written into the torrent file). The hash is used by trackers and peers to identify the torrent when communicating. The 'info' section contains a list of entries - according to the torrent specification these entries must be sorted into a specific sequence. This order is important when calculating the hash. Unfortunately, either due to bugs in the torrent creation process, or erroneous post-processing of the torrent, there are malformed torrents in which the entry order is incorrect. This can result in a tracker (for example) calculating one hash for the torrent and a client (Vuze for example!) calculating a different one. When this happens the client will attempt to contact the tracker to obtain peers and the tracker will most likely respond with 'unknown torrent'/'unauthorized torrent' (as the hash, from its perspective, doesn't exist).
From Vuze 4703_B23 onward, code has been added to detect when the order of these elements is incorrect and raise an alert - indeed, this may well be why you're reading this page.
If you get this warning, check the torrent within Vuze to see if it is either getting an error from the tracker (you may need to go to the torrent's 'detailed' view and select the 'sources' tab to see the error), or there are no other peers (or very few) available (a sign that the incorrect hash has created a split swarm).
If this is the case you can use the tool that has also been built into Vuze to try and fix the torrent.
Go to the Help menu, select 'Advanced' and then the 'Fix corrupted torrent...' option. Browse to the suspect torrent file and select it. If the tool reports that it has fixed the hash, save the corrected torrent, remove the existing (incorrect) torrent from Vuze and add the fixed one.