We've been having the same problem on centos 5.8, with a 2.6.18-308.1.1.el5 kernel. It locked up twice and became unresponsive and had to be rebooted. After it came back up we discovered a number of instances of the 'task blocked' message - happening several times a day. We reflashed the raid controller's firmware last week, and the box has stayed up since. I was about to declare victory when I double-checked the logs and found that we got three 'task blocked' messages overnight. The times of the messages match up with the times that we were transferring large iso images to the box. Ali