I had a problem during the upgrade to 7.5.3 which left my system totally down (i.e. all apache vhosts configs hosed, so 100 sites where down). I fixed it as follows (I may write this up into a detailed howto at a later date, here's the cliffsnotes version).
First of all, remove all plesk rpm's, start by doing a
rpm -qa | grep psa
to get the main ones, then you need to remove ones that depend on psa, so that's
rpm -e psa-api-common psa-api-cli psa-api-rpc --nodeps
now try
rpm -e psa
you'll get a load of dependency errors, simply add all of these to the list, i.e.
rpm -e psa psa-migration-manager psa-bu etc. etc.etc
You may get a load more dependancy errors, these are mostly application vault packages (if you have them installed not a good idea as i doubt they get timely security updates), add those to the list too. if you still get errors add a --nodeps to the end at this point.
Now comes the fun part, you need to restore the psa database (mysql database where plesk stores hosting data) to the last good dump (plesk makes a dump of all databases every night). The files are called mysql.daily.dump.X.gz where X is the age (in days) of the dump, get the last known good dump (i.e. if the problems started 3 days ago after the dump file was created get mysql.daily.dump.3.gz, in the following example that's the one we'll use.
cd /var/lib/psa/dumps
cp mysql.daily.dump.3.gz /tmp
cd /tmp/
gunzip mysql.daily.dump.3.gz
Now we need to remove the current databases (may have been left in an inconsistent state by the autoupdater that for some reason best known to SW-SOFT simply borks at errors instead of backing out and restoring the system to the previous working state, but that's a rant for another day)
So, the long and the short of it is you need to lose the horde and psa databases, launch the mysql admin tool:
mysql -u admin -p`cat /etc/psa/.psa.shadow`
DROP DATABASE horde;
DROP DATABASE psa;
quit
(the ; is important as it signals the end of the command.)
Now we need to reload the working db
mysql -u admin -p`cat /etc/psa/.psa.shadow` < mysql.daily.dump.3
now go and get the autoinstaller for 7.5.2 (or do a yum install psa via Atomic Rocket Turtle's yum archive which IIRC still has the 7.5.2 rpm's) and all should be good.
As always when trying to fix sw-softs installation issues, YMMV.