The main issue was blogged by Daniel Nashed on his blog , and occur sometimes with SSO configurations. The root cause was the Fix Pack not updating the file 'server' on all Unix platforms and 'nserver.exe' on Windows platforms. (SPR RSOI9Y7BZW).
In this IF1 is addressed also the SPR CSMH9M2JXL that cause an extra logging about ICAL messages conversion.
IBM will post a repack of FP4 between July 14th and 15th that will include this 2 fixes.