while i would like to assume that you have tried everything i would just like to confirm this. with both the remote working on the tv and the buttons present on the tv and the fact that there is no external decoder or remote. if all of this applies please make sure to add this to your question as this clarifies this a person who might know where it is that the problem lies. even forgetting to put charged batteries in the remote can happen to the best of us.
-M