There is an ia64 kernel bug introduced in 2.6.7, which may lead
to hang on boot. See
for details and possible patches.
2.6.7-1.441 is OK. 2.6.7-1.448 and and 2.6.7-1.457 both hang on my
Kernel 2.6.7-1.469 booted fine on ia64.
2.6.8-1.603 is OK.