ATA problem in Parallels: warnings -> failures

Dear Soren,

Since my most recent kernel update, the intermittent TIMEOUT - READ_DMA 
warnings I get on my parallels install appear to have become somewhat less 
innocuous:

ad0: TIMEOUT - READ_DMA retrying (1 retry left) LBA=38669679
ad0: FAILURE - already active DMA on this device
ad0: setting up DMA failed
g_vfs_done():ad0s1e[READ(offset=18188230656, length=2048)]error = 5
cvs update: in directory modules/tx:
cvs [update aborted]: cannot read CVS/Repository: Input/output error

In the past, this appeared to be a symptom of long and unexplained delays in 
Parallel's ATA -> image file operation, but were not harmful as the retried 
operation succeeded.  However, it seems that this is no longer the case, with 
errors exposed to higher levels of the file system.  Do you have any 
suggestions?

Robert N M Watson
Computer Laboratory
University of Cambridge