Why this is happening can depend on things from what version you are using, what IDE you are using, what properties you have set, etc. The quickest way to solve this issue is to do a web.config redirect and to copy your images local to your application. Here is a KB article to achieve this:
http://devcenter.infragistics.com/Support/KnowledgeBaseArticle.aspx?ArticleID=6158
If you tell me your NetAdvantage version and CLR, Visual Studio version, and the aspx markup of one of your problem controls, it will help in determining the cause of your issue.