Hi Bruce,
Thanks for the quick reply.
To answer your questions, the extension was installed on the second machine using a signed vxp file.
I have solved the mystery, and it was my fault.
When testing the extensions on my local machine, I use hard links from the adobe extensions directory to my local development directory.
The unresponsiveness of the extensions in the 2nd machine was due to javascript error on the extension page (it would be wonderful if adobe premiere could give us a log of such errors instead of silent error).
The ultimate cause turned out to be that when installing the extensions using vxp extension package, adobe was creating directory names based on the extension manifest file, which is very sensible, but my extensions were looking for each other (I know this is a weird thing to do but they do this for shared code purposes) using different directory names.
I should have tested it myself on my development machine and I would have caught the problem -- totally my fault.
All working well now (if anyone is curious here are the extensions on github: https://github.com/dcmouser/jrPremiere )
Thanks,
-jesse