Under Redhat 6.0, it appears that pcmcia card services
3.0.9 can cause the system to lock during the boot process
on a Toshiba laptop (ToPIC 95/97 PCMCIA chipset). It
appears to occur when the following conditions are met:

1) there are no cards inserted on bootup, and
2) a "pre-install" line for pcmcia_core exists in
conf.modules.

The conf.modules line specifies that pcmcia_core is set to
load /etc/rc.d/init.d/pcmcia start. This appears to have no
effect when a card is inserted while the boot process
continues... however, if no card is inserted, the presence
of this line will cause a hard lockup.

The line in question is:

pre-install pcmcia_core /etc/rc.d/init.d/pcmcia start

This may be because the pcmcia_core module is set to load
inside that script as well. (loop?)

Several of these lockups (and subsequent forced reboots)
caused major filesystem corruption because fsck apparently
did not notice the dirty state of the filesystem on reboot
and attempted to write past the end of volumes.

Removal of this line fixed the problem satisfactorily. The
pcmcia_core module loads when the first card is inserted.