I'm trying to install ZDesktop on Ubuntu 9.04. I was able to install and run ZDesktop on Ubuntu 8.10 without any problems.

harlan:~/download/zimbra$ ./zdesktop_1_0_2_build_1652_linux_i686.sh
Unpacking JRE ...
Preparing JRE ...
./zdesktop_1_0_2_build_1652_linux_i686.sh: 251: bin/unpack200: not found
Error unpacking jar files. Aborting.
You might need administrative priviledges for this operation.

I've even tried running this as root, getting the same error. Please let me know what other information you need.