RealPlayer is designed to work very large libraries. There could be various factors causing this.
- A bad/corrupted file or files within your library.
- An incompatible file or files within your library.
- A bad installation of RealPlayer.
That being said, can you please let us know how large is your library? Roughly how many files are we talking about? And are these files stored in your PC's hard disk or in an external drive?
To make sure you are not having a bad installation of RealPlayer, please follow the instructions from the below link to resolve your issue.
Please note: If you have any playlists created, you will have to recreate them.