| I had a bass where some of the frets had popped out at one end. To fix this, I pressed the frets down hard (one at a time) with a steel bar, and, having previously masked off the relevant part of the f/board, ran a line of superglue down the fret/f/board line. If you use the thin, runny, version, it wicks down into the cut in the f/board, and as long as you hold the fret in position until it goes off, you're done. This has lasted two years so far, with no sign of movement.
If you do it, run masking tape down the line of the fret, either side,but leave a tiny gap for the glue to run into, and don't get it on your f/board, because it's a swine to get off!
Make sure you hold the fret down hard in it's slot before you start, as it goes off very quickly. | 
