If you experience that, make sure you are encoding your request properly. For example http://api.linkedin.com/v1/people-search:(people:(id,first-name,last-name,picture-url,headline,location:(name)),num-results)?keyword=" + HttpUtility.UrlPathEncode(user.FullName).
In the above example if the user full name is Pavel Donchev, if you use HttpUtility.UrlEncode(user.FullName) the result will be Pavel%Donchev.
It should be Pavel%20Donchev, which is result of calling HttpUtility.UrlPathEncode instead HttpUtility.UrlEncode.
Almost unnoticeable difference mixed with generic message that may cause lots of head aches for you.
