IDE messages from the kernel question

["Igor S. Livshits" <igorl life uiuc edu>]

Hello,

I found these messages from the kernel this morning:

kernel: hda: irq timeout: status=0xd0 { Busy }
kernel: hda: disabled DMA
kernel: ide0: reset: success

What may have caused these, and why would DMA have to be disabled? 
THe machine has been up for over a week otherwise. It's running 
kernel 2.0.36 and RH 5.2

Thanks, Igor