Source Atapi/EventID 11

Can anybody help me with my PC is getting several of these Error
messages at a time? They have an error description of "The driver
detected a controller error on \Device\Ide\Ideport2." They only started
around a month ago and I haven't made any hardware changes.

The symptom is that the PC will basically freeze up.

I can see several hits from Google (not much help from Microsoft's
support) referring to low power supply, motherboard issues, hard drive
but nothing definite.

I'm replying to myself as I didn't get any other responses and in case
it helps anyone else.

I eventually tracked this down to a fault with one of my two DVD R/Ws.
I disconnected it at the motherboard and now no more ATAPI errors and
frozen computers.

Hooray!

I'm adding a second update as the dreaded Atapis started again.

I took the PC back to where it had been rebuilt (new motherboard/hard
drive). Visata was reinstalled and I was told the problem had ceased.
The day after I got it home, they started yet again. These errors make
the PC unusable and unless you have a spare hour or two to wait them
out, you end up turning off the power.

So this is what I did. The PC is out of warranty and pretty useful as
it is. Despite being a techno-dork, I -

1. Disabled all the "basic" lines under the IDE ATA/ATAPI part of
device manager.
2. Shut down.
3. Opened the case and disconnected the ide/atapi ribbon from the
motherboard and the optical drives.
4. Booted.
5. Shut down.
6. Reconnected the ribbon.
7. Booted and enabled all the items in 1 above.
8. Rebooted.

I have had no atapis for 5 days and there are a lot less error messages
in the event log than previously. The optical drive works fine.

Hope this helps anyone else in the same boat.