Thanks for your help Madhura. You're right. If you ignore that rather terminal looking error message, the build and package functions work regardless.
Do you know if that error will go away in the next release?
I have a related question about compiling for a 32 bit target machine... I can use 'deploytool' from a windows command line to build the 64 bit version of the program, but when I add the '-win32' argument to the same command it returns 'Unable to find a suitable install area'. Any ideas?