I have still the same problem too, playing Kontakt samples from a slave, but only on playback, not while recording or playing midi. When I run the same template in VE Pro standalone, and send midi via MidiOverLan, or hardware midi, there are no hanging notes, only in server mode via ethernet audio. Most of the time it's fine, but then suddenly some notes start to hang. One odd thing that I noticed is that it only happens to me when I do 4-5 part writing with quite independent voices. Block chords are never a problem. The slave also runs a lot of VSL instruments with no problems.
host: Logic 9.1.1 (in 32 bit mode), VE Pro 6150, Mac Pro Intel 8 core, 10GB RAM, Mac OS 10.5.8
slave: 11 instances of VE Pro 6150 (64 bit server, multiprocessing 1 thread per instance) , Kontakt 4.1.0 (multiprocessor support disabled) , running Spitfire Audio library, Windows XP64, quad core Xeon 24GB RAM
Karel, would it help if I sent you the Logic file in question (I could mark where notes hang) and the corresponding Vi frame file (you'd have missing Kontakt instruments though)?