The only thing you could do is to reset Smart Hub or Internet@TV. If you have a model number, I can tell you how to go about doing so I suspect that it may be an update to the app, though, and either they removed the functionality for some reason, or they accidentally broke the code for it.
after i launch youtube app, while I type letters in search, earlier, I used to get next letter as suggestions on four sides of the letter i typed. But now am not getting those suggestions. can some one pls let me know how can i get them back. thanks