Problem happened even with hpet=disable. Syslog for the whole session attached. The mouse cursor shape changed to a vertical dotted bar (like a rebar handle) a few moments before the freeze. (Actually, since 2.6.25 I experience random cursor shape changes fairly often, don't know if this may be related at all). I must also add that when there is intense disk activity (e.g. searching for a file in a large directory tree in konqueror, or when after updating the package list in synaptic) the system is completely unresponsive (have not checked if this is due to hpet=disable).
Attachment:
syslog2.gz
Description: GNU Zip compressed data