We have 3 ThinkCentre machines (model 8085) which exhibited the same behaviour. BIOS upgrades were unhelpful as above, as was commenting out the ACPI Sleep functionality in the config. Kernel source is tracking this bug (with a fix that worked for me on unstable/2.6.10) as follows: http://bugzilla.kernel.org/show_bug.cgi?id=4235 brian.