You could try reinstalling iReal b. First, create a playlist (or several - maximum of about 100 songs each) to backup to email (forum playlists can be downloaded again so backing up these is not necessary.) Delete the app, then reinstall via the Market. There are some exercises within the app so you could test with those. Restart your phone again.
Are other audio apps ok?
You could also test with turning off wireless/3G etc. or other apps that might be working in the background.