Sounds like your default player got changed. It may have gotten changed if you've downloaded a new player or program lately.
Try this to change it back(you may need to do this with each file type you want changed, audio, video, ect).
Open your shared folder outside of LW. An easy way to do that is to go to the library page in LW, hi-lite the shared folder then click the explore button (below the library folders window).
Then right click on one of your files > then click on "Properties" > then where it says "opens with" click on "Change". A box will open, click on "Real Time Player" then click OK. Then click apply then OK. That should change the default player back to RTP.
See:
Setting default audio program (click on link)