AFAICT, UiBinder in GWT 2.4 generates a SafeHtmlTemplates (instead of building an HTML string by appending to a StringBuilder, as was done in previous versions). This means that everywhere you have a "replaceable" part (e.g. {foo} in an attribute, or a widget or <ui:msg>) it will generate a placeholder in the @Template and an argument to the template method. It seems like you have more than 255 such "replaceable part".
Maybe you could pass -gen to the Compiler and look at the generated code? It might be worth filing a bug, attaching your UiBinder template (or any template that would reproduce the issue).
As a workaround, you can throw an HTMLPanel in place of a few HTML elements, to reduce the size of the template (if I correctly guessed, that would split the template in several small templates, one for each HTMLPanel)