selenium-webdriver 2.5.0 error

     Selenium::WebDriver::Error::InvalidSelectorError:
       The given selector "./descendant-or-self::*[contains(normalize-space(.), 'Who are you? Question number 1')] is either invalid or does not resultin a Webelement. The following error occurred:
       [InvalidSelectorError] Unable to locate elements with the xpath expression ./descendant-or-self::*[contains(normalize-space(.), 'Who are you? Question number 1')] because of the following error:
       [Exception... "Component returned failure code: 0x80070057 (NS_ERROR_ILLEGAL_VALUE) [nsIDOMXPathEvaluator.createNSResolver]"  nsresult: "0x80070057 (NS_ERROR_ILLEGAL_VALUE)"  location: "JS frame :: resource://fxdriver/modules/atoms.js :: <TOP_LEVEL> :: line 2360"  data: no]
     # [remote server] file:///tmp/webdriver-profile20110824-22465-be82oi/extensions/[email protected]/components/driver-component.js -> file:///tmp/webdriver-profile20110824-22465-be82oi/extensions/[email protected]/components/firefoxDriver.js:466:in `unknown'
     # [remote server] file:///tmp/webdriver-profile20110824-22465-be82oi/extensions/[email protected]/components/driver-component.js -> file:///tmp/webdriver-profile20110824-22465-be82oi/extensions/[email protected]/components/firefoxDriver.js:507:in `unknown'
     # [remote server] file:///tmp/webdriver-profile20110824-22465-be82oi/extensions/[email protected]/components/nsCommandProcessor.js:306:in `unknown'
     # [remote server] file:///tmp/webdriver-profile20110824-22465-be82oi/extensions/[email protected]/components/nsCommandProcessor.js:320:in `unknown'
     # [remote server] file:///tmp/webdriver-profile20110824-22465-be82oi/extensions/[email protected]/components/nsCommandProcessor.js:197:in `unknown'
     # [remote server] :0:in `unknown'
     # ./spec/acceptance/psychotest_spec.rb:30:in `block (3 levels) in <top (required)>'
     # ./spec/acceptance/psychotest_spec.rb:29:in `each'
     # ./spec/acceptance/psychotest_spec.rb:29:in `block (2 levels) in <top (required)>'