The use of agents that are installed on both 32 bit and 64 bit operating systems is not recommended.  Where possible we recommend that environments are comprised of totally 32 bit or totally 64 bit machines to rule out any unnecessary complexity.  

The main reason for this is that applications on a 64 bit operating system may be installed into "Program Files (x86)" folder as opposed to "Program Files" as with 32 bit operating systems.  This can result in issues where hard coded paths to resources such as JDK folders, classpaths or data files are specified.

Where it is not possible to have all agent machines the same you can work around the problem by installing any applications that Silk Performer relies on (such as JDK, Citrix ICA etc.) in a common directory like C:\applications etc. and then point Silk Performer to this directory to look for the files.