Tapestry 4 localization problem

I decided to add localization to my web application. I created file .properties, where I added some pairs : key - value. When I again entered on some of my pages - exception happened : No message found under code 'alt' for locale 'ru_RU' (org.springframework.context.NoSuchMessageException). This problem occurred cause to DatePicker component, which wanted to find localization parameter called "clear" and couldn't find it in .properties file. The simpliest solution for this problem was to all fictive parameter called "clear" with any value (for instance, "CLEAR"). In finding the root of this problem I didn't succeed.