I would not be surprised if it was a mistake. I would suggest changing IE version from 64 bit → 32 bit or vice versa to check.
, 10.0.11 (12 2013 .), . , , , .
, . downcase/lower . -
random_username = "John"
lowercase_username = random_username.lower()
lowercase_username
this.driver.FindElement(By.Id("uid")).SendKeys(lowercase_username)