The above doesn't look like what you intend to do, you are sending an ENTER keystroke to the logout element, waiting for 0.5 seconds (no need to wrap that in a try / catch as the sleep should not fail to execute), then you are moving the mouse to the element and then trying to click it.
Only one of the above should be necessary if this is a normal button or link, and it should be possible by simply calling click().
Please let us know what exception is thrown if you call:
WebElement element = ((WrapsDriver) selenium)
If an ElementNotVisible exception is thrown, or more than one element was found, you may be trying to interact with a hidden element, so make sure this is the only logout element matching your XPath, and that this one is visible - the Firefox plugin 'XPath Checker' is very useful for writing and checking XPaths in real time.
It may be useful to write some debug information to the console if you are still stuck. If element.Displayed is false, WebDriver will not be able to click it, so you know you are trying to click the wrong element if you can see it at the time.