I reported this a while back... I'm using VE Pro on 3 different Macs, and this problem occurs on all of them, even on the simplest setups (1 VSL instrument loaded). When I try to insert an AU effect on any instrument channel or output, the VE Pro server instantly crashes. This is on both 32 and 64-bit server versions.
Hopefully the wizards in Vienna can give this some serious attention for the next update since this is half of VE Pro's functionality - the whole idea is to get as much processing done in VE Pro as possible!
Sending a crash log to support...