I also experienced trouble with IPS on CU189.
I have a webserver running in DMZ with a pinhole to MySQL in Green.
IPS is enabled on red, orange and blue.
After upgrading to CU189 the webserver in DMZ was no longer able to contact the MySQL DB in Green.
After a few hours of checking firewall rules, logs, tcpdump etc… I somehow accidentally bumped in the Intrusion Detection webUI page, and tried unchecking monitoring orange…
And suddenly the webserver could again contact MySQL.
So now I had to disable IPS on orange