I finally decided to do a Kubuntu 10.04 LTS fresh install, so I started it from LiveCD (no errors found) with normal kernel parameters. Everything is fine, KDE starts up and I can mount my disks. But before installing, I wanted to check dmesg just to be sure and there I found some errors like these:
ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
ata1.00: irq_stat 0x08000000
ata1.00: failed command: READ DMA EXT
ata1.00: cmd 25/00:08:01:66:f4/00:00:1b:00:00/e0 tag 0 dma 4096 in
ata1.00: status: { DRDY ERR }
ata1.00: error: { ABRT }
ata1.00: configured for UDMA/100
ata1: EH complete
which did NOT show up in my Karmic system (using kernel 2.6.31-22-generic-pae as I'm typing). I'm also affected by bug #228302 from Feisty (which, since Intrepid, I'm used to work around with the "pata_ali.atapi_dma=1" solution), so I thought this was some kind of libata regression. I googled around a bit and tried starting up my LiveCD with many parameters such as "noapic acpi=off pata_ali.atapi_dma=1" but I still get the errors, no matter what. As far as I used the LiveCD session, I noticed nothing unusual, but I'm too scared that after the installation my system could freeze due to interrupt losses, leading to data loss, so I'm still on Karmic right now and sincerely wish to know what's behind these errors, before knowing if there's any fix.
I'm attaching my dmesg output from my Karmic installation, as well as the concerning Lucid ones.
It's easily reproducible on my hardware, just insert a Lucid LiveCD and look at dmesg output, thus I put this bug status to Confirmed. And one more thing: S.M.A.R.T. status is ok, I get this errors just on Lucid!