Same problem
I had the same problem however was charged by Parallels support as they said Plesk did not cause this, however its the only thing we did that could have broke it.
To resolve the issue they charged us $75.00 to do the following after they found some files missing:
/etc/init.d/qmail stop
/etc/init.d/xinetd stop
rpm -Uvh --force psa-qmail-1.03-fc6.build86080722.00.x86_64.rpm
/etc/init.d/qmail start
/etc/init.d/xinetd start
Now I have found somebody experiencing the same problem I will be taking this up with Parallels support.
I now just need to know the commands required to update to patch 5 for 8.6.0 before I try to install version 9 again. As I had the following error:
error: Failed dependencies:
psa-hotfix4-8.6.0 = 8.6.0 is needed by (installed) psa-hotfix5-8.6.0-8.6.0-fc6.build86080930.03.x86_64
ERROR: Unable to install the requested packages because either there is not enough free disk space left, or there are package dependency problems.
Warning! Not all packages were installed.
Please check if your system services are operable.
Please, contact product technical support.
any ideas of how to fix this
Thank you for any help.
Terry