Nero Smart Start: Can only use drive once for ripping

I am using a Windows XP computer. I start Nero StreetSmart with the intention of ripping tracks from a music cd onto my hard drive. When I put a music cd into my cd/dvd drive, I am asked to choose a drive (from within Nero Smart Start). I choose the drive where the cd is located and I am able to continue to the next screen and rip tracks from the cd. It is then that I have a problem as follows: When I remove that music cd from the drive and put another music cd in the drive, a screen again appears asking for me to choose the drive. When I choose the same drive (as the first time that I ripped songs from a cd in that drive), a message box appears stating that the drive is in use by a program, and I am prevented from continuing to the next screen. This message box (“drive is in use…”) appears only after I use the drive one time in Nero Start smart and then try to use the drive again to rip songs from a different music cd. I do not get that messaage box (“drive is in use…”) if I choose a different drive.
Why do I get that message box that the drive is in use, after I use the drive one time with Nero Smart Start? How can I prevent that message box from appearing, so I can use that drive again with Nero Smart Start for ripping songs from another cd?