Michel,
More experimenting with BB browser configuration changes and I found another combination that makes a difference. The browser configuration item "Content Mode" has 3 choices, HTML only, WML only, WML & HTML.
With Content Mode set at HTML only, disabling JavaScript allowed my BB to successfully communicate with the ISY. Enabled JavaScript caused comm errors.
With Content Mode set at WML & HTML, the state of JavaScript did not matter, the communications were SUCCESSFUL whether enabled or disabled.
Do you use any WML in your scripts?... still confusing, but I feel I am getting somewhere.
Cheers!
Dave