What happens when you disable LW's player (tools > options > player) & use a different player?
Also try playing songs from your saved folder, rather than through LW... go to LW's library, click on Saved Files, highlight a song & click Explore. Your saved folder will open - in that saved folder, right click on a song > open with > choose whatever player.

If songs won't even play that way then maybe they're bad files. Check out these links for more info.
Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see)

* WARNING: Viruses on network you should be aware of ! *

Fake files showing up in search results

How to find music


And this one might help with your music not showing up: If you've updated LW and can't find your downloads!
Check in the different saving locations & see if your files are there