Installing PS5 (126.96.36.199) can cause some problems when using Oracle XE as the infrastucture database. The solution is described in this SOA Suite / BPM blog by Niall Commiskey.
More tips on upgrading OFM 11g to patch set 5
More considerations on upgrading to OFM 188.8.131.52.0
There is an additional article on upgrading to OFM 184.108.40.206 on the Whitehorses blog. It goes into more detail on JDK 7 support, OWSM in SOA Suite, the combination of OSB en OWSM and for example the PSA (Patch Set Assistant) performance.
Java memory arguments in OFM 220.127.116.11.0
More on setting Java memory arguments in SOA Suite 18.104.22.168.0.