Power Mac G5 Card Reader Won’t Eject Media

I’m having a problem with the Power Mac in our Marketing Department. When trying to eject a memory card from the reader or a CD from the CD drive, a message is displayed saying “The disk is in use and could not be ejected”. I have limited troubleshooting experience with Macs so any suggestions would be appreciated.

The card reader is an iogear GUH284R USB hub and card reader.

Thank you.