Some songs suddenly won't play, import or convert!

Question

I recently transfered my mp3's from my PC to my Mac with my USB disk. I also transfered the Album Art folder and the two iTunes Library files, so I can keep the "Date Added" and other personal preferences.
Now, however, I cannot play certain songs that I've ripped from CD's. When I click the file in iTunes, it simply does nothing (apart from showing the small Apple logo in the little screen at the top). I also tried to play the same songs on my PC, and suprisingly, they do not play there either. I have played these songs before - many times, and have never come across any issues. Most are ripped in late-June and July from my PC, so not that recent. Others ripped after that - work.
I have the latest version of iTunes on my Mac, but not on the PC (7.2.0.35). They play in QuickTime, Windows Media Player and whatnot, so I believe that the problem is with iTunes.
When I try to re-import them to my library - they do not import. When I try to convert them to mp3 with iTunes - I get an "unknown error (-50)" message. When I "Get Info" about them, they show up fine, apart from that in the Summary tab, the whole right column of information is not displayed (where it would say Format, Channels, ID3 Tag, Encoded with). It is however identified as an MPEG audio file, of a certain bit rate, sample rate etc., and even it's play count remains.
I had a few old saves of my iTunes Library, so I tried re-importing the songs with those - no success.
I have no way of knowing which songs are unplayable in this way, because no "exclamation mark" thing appears and they are simply skipped in random play or party shuffle and playlists.
Also, when the song is selected, and the album artwork box in the bottom-left corner is open - it displays "Album Artwork Not Modifiable" for these unplayable songs.
I hope you can help! Thanks in advance

Answer 1

I have had the same problem, and managed to solve it this evening. This solution works on a PC, so if you also have a Mac you'll need to copy the repaired tracks across somehow.
The cause of the problem is faulty ID3 tags - the area inside the MP3 file where metadata such as artist name, album title and cover art are stored. iTunes has known issues with the insertion of cover art into ID3 tags, and given that you and I have both noticed the unreadable/unmodifiable album art, I suspect this is where the problem lies. iTunes appears to have broken the files sufficiently that I couldn't get them to play in any music playing software, or on my iPod itself. On the iPod, each song is attempted for a couple of seconds and then skipped.
So much for the problem. Here is the solution:
What you will be doing is to strip out and then re-write all the ID3 tags. Note that I tried other software, which was meant to do exactly that, with no success. The program I ended up using had an option to rewrite MP3 tags, which also didn't work. The only successful method was to tell it to remove the tags altogether, and then tell it to re-write them from scratch. So here is the step-by-step method for fixing a single song, and then the shortcut for fixing the lot:
1) Find and install a freeware program called "foobar2000". I got version 0.9.4.4. Other versions may have slightly different user interfaces. Although I could not find this download from my usual trusted download sites, I ran a spyware check afterwards and it was clean.
2) Start foobar2000.
3) Find one of your broken MP3s and drag-and-drop it into the foobar2000 window. You can drag it straight out of the iTunes window, rather than having to find the file on your hard drive. (NB if you're nervous, locate the file on the hard drive first and keep a safe copy while you do this.)
4) In the foobar2000 window, right-click the file, and choose "Tagging... MP3 Tag Types..." from the context menu.
5) Now untick ID3v1 and ID3v2, and choose "Update Files". This step strips out all the ID3 tags.
6) Now go through the same menu options and tick ID3v1 and ID3v2 again, and choose "Update Files". You may find that ID3v2 is already ticked, which is fine. This step re-writes all the ID3 tags. In between Step 5 and Step 6, your ID3 tags are stored inside the foobar2000 program and nowhere else. Don't exit foobar2000 until you have re-written the tags. Re-writing seems very much faster than removing the tags.
7) Finally, go into iTunes and double-click on the tune to make iTunes start playing it. It should now play fine! Moreover, iTunes will now notice that the ID3 tags have changed, and will queue the track for upload to your iPod at the next sync. No need to play the whole track. Just starting to play will work.
So far so good. One track converted. Pull up the foobar2000 window, left-click the song you fixed, and hit the delete key to remove it from the queue. Now for the shortcuts:
Album-at-a-time: Find a faulty album, select all the tracks in the iTunes window (click the first track, SHIFT-click the last). Drag and drop them into the foobar2000 window. Use CTRL-A to select all the tracks in the foobar2000 window. Do steps 4-6 above. Do step 7 above for each song, or just start playing the first track in iTunes and repeatedly click "fast forward" to skip through the rest.
Many albums at a time: As above, just drag and drop several albums, one after the other, into the foobar2000 window before you repair the tracks.
I suppose you could "repair" all the tracks in your iTunes, even if most of them are not broken. This way you wouldn't need to track down the broken ones... just use CTRL-A in iTunes to select the lot, and dump them into foobar2000. But I don't know how many tracks foobar2000 will handle. Try this at your own risk, but please report back if it works.
Also, note there is a quicker way of making iTunes realise that you have repaired the tracks. Instead of playing each track, just right-click, go to "Get Info", and go "OK" +without changing anything+. Note that this works for multiple songs in one go, if you select more than one song. I repaired about 1000 songs, and then in iTunes went CTRL-A (to select all), "Get Info" and "OK", and it happily re-read all my ID3 tags in a minute or so, thereby covering all 1000 that I had repaired, and marking them for syncing. Note that any changes you do make in the Get Info window will be put through onto every single track you have selected. So just hit OK, nothing else!
Now just plug in the iPod and wait for it to sync, and you're done.
Finally, you may notice that some of your album art is now missing. This is the price you pay, unfortunately. The art was the problem in the first place, and was not salvageable. This way at least you quickly and easily get your music back, and retain all your tagging and playing info.
Sorry for such a long post. It took me a while to figure out, and I know a lot of people will be looking for this very answer.
Good luck!
PS there is a third type of tag called APEv2. A very few of my tracks had this, and because I was repairing hundreds of tracks at a time, I don't know which ones. I just left the APEv2 box untouched, but I don't know if that's sensible. Anybody care to report back?