I have and Iomega Zip Drive (100, Parallel) connected to my
home workstation.  After upgrading from Red Hat 6.0 to 6.1,
I can no longer load the 'ppa' kernel module which is needed
to use the drive.

To test the problem, I set a new, fresh install of Red Hat
6.1 on a different PC (at work, had a different Zip drive
attached, but same model.)  I had the same results:

when I run 'dmesg' after system startup, there are no ppa,
parport or scsi messages listed.  'lsmod' initially shows:
Module                  Size  Used by
3c59x                  19112   1  (autoclean)
nls_iso8859-1           2020   1  (autoclean)
nls_cp437               3548   1  (autoclean)
vfat                    9180   1  (autoclean)
fat                    30464   1  (autoclean)[vfat]

I then run:
[root@computer /root]# modprobe ppa
/lib/modules/2.2.12-20/scsi/ppa.o: init_module: Device or
resource busy
parport: Device or resource busy
[root@computer /root]#

'dmesg' then shows:
ppa: Version 2.03 (for Linux 2.2.x)
ppa: parport reports no devices.
scsi : 0 hosts.

now 'lsmod' shows:
Module                  Size  Used by
parport_probe           2980   0  (autoclean)(unused)
parport                 7124   0  [parport_probe]
3c59x                  19112   1  (autoclean)
nls_iso8859-1           2020   1  (autoclean)
nls_cp437               3548   1  (autoclean)
vfat                    9180   1  (autoclean)
fat                    30464   1  (autoclean)[vfat]