I recommend you switch from ImplicitlyWait to Explicitly wait for the element you want as detailed at http://www.seleniumhq.org/docs/04_webdriver_advanced.jsp
Example:
require 'rubygems' # not required for ruby 1.9 or if you installed without gem
requireWebDriver 'selenium-webdriver'
driver = Selenium::WebDriver.fornew :firefoxFirefoxDriver();
driver.get ("http://somedomain/url_that_delays_loading"
);
waitWebElement myDynamicElement = Selenium::WebDriver::Wait.new(:timeoutnew =>WebDriverWait(driver, 10) # seconds
begin)
element = wait.until { driver(ExpectedConditions.find_elementpresenceOfElementLocated(:By.id => "some-dynamic-element"("myDynamicElement") }
ensure
driver.quit
end));