Having a strange issue that I have been unable to resolve.

Running Network 6.5 SP4a servers, Zenworks 6.5 SP2a with ZFDAgent 6.5.1 on
the XP PCs that run NALWIN32 on startup.
Citrix environment is Windows 2003 Server & Presentation Server 4.0 with
latest Presentation Server support pack.
We have created many application objects, both non-citrix and citrix,
delivered via the NAL. Having problems with just the Citrix Published
Application icons which will intermittently not respond. Double click,
right click verify/run and the icons does nothing, no error. Wait a
minute and it works. Sometimes if existing Citrix applications are
running, closing them will make the applications that would not previously
work magically start working? This problem is intermittent however quite
reproducable sitting at a PC and trying one Citrix application after the
other to launch the citrix applications using NAL icons. Using Citrix
Program Neighbourhood I am unable reproduce the problem where the
application will not launch.

Any suggestions on next course of action?