Hi John,
Welcome to the forum.
Q1. Once you delete an atist or an album then it/they is/are gone, unless you have a backup to copy back from.
This raises the question of having a backup of your music; if you haven't done an 'Export' to a USB backup device, please do this ASAP otherwise you could lose your valuable music collection at any time. The Brennan is a computer system and, like any computer system, it can behave unpredicably, with the total loss of data being one of the end results.
Q2. It is unlikely that there is a CD stuck in the unit if you can insert other CDs, but refer to Q3 below.
Q3. What version of B2 software are you running on? To find out, using the B2 remote control, press the 'Info' button twice and the 'Version' should show on the display panel. If you post this here, then we can give you further advice.
Regards,
Peter.