Description of problem:

Watch this:

# yum install hplip.x86_64
....
Downloading Packages:
(1/1): hplip-2.7.6-1.fc8. 100% |=========================| 9.8 MB    02:22
.....
Transaction Test Succeeded
Running Transaction
error: %pre(hplip-2.7.6-1.fc8.x86_64) scriptlet failed, exit status 1
error:   install: %pre scriptlet failed (2), skipping hplip-2.7.6-1.fc8

Installed: hplip.x86_64 0:2.7.6-1.fc8
Complete!
# rpm -q hplip
package hplip is not installed

Putting aside a problem with yum which claims that it installed
something while this is not really true (see bug 186945) the problem
is really here:

# rpm -q  --scripts hplip
preinstall scriptlet (using /bin/sh):
# No daemons any more.
[ -x /etc/init.d/hplip ] && /sbin/service hplip stop

That script fails if /etc/init.d/hplip does not exist or, possibly,
when it was not running.  Adding 'exit 0' in the next line would
cover all contingencies.

Version-Release number of selected component (if applicable):
hplip-2.7.6-1.fc8