It's really strange, I tested with other song and happen a similar thing: the song was in "karaoke", then I moved to another and back to the first, and now it's only in text-mode, but then never back to "karaoke", even if I restart winamp.
Then I took a look to database and there is only text-mode versions of both songs. I run database checks every two-weeks, sometimes find some minor errors, but never lost a lyrik before. I guess is time to make more backups, thanks for noticing that

Maybe the lyrik still have in cache the "karaoke" version in your computer, that explains why it shows and then go back to text-mode.
If it continues happening to your songs, please do a right-click > Lyrik > Edit > Next... > Internet
It will send the lost karaoke version back to database.
I tested with many other songs, and this problem didn't happened again, for good it is just for a few songs.
Thanks again,
Willian