This is similar to http://javafx-jira.kenai.com/browse/RT-18180 as it seems to affect just the FXML-login demo launch in jnlp/plugin mode only. When CSS-to-BSS conversion is enabled (we discovered the bug in NetBeans 7.1rc) than the demo fails to launch in jnlp/plugin mode. When CSS-to-BSS coversion is disabled (i.e. with standard CSS only) it seems to work fine (provided signing is on as reportontent-Disposition: form-data; name="summary"

FXML login demo with CSS converted to BSS fails to launch in jnlp/plugin mode