I have recently upgraded my project from Infragistics netadvantage 2005 volume 3 to 2008 volume 2. The webpanel which was working fine with the older version is not working properly after the upgrade. The look is different now and the image at the end of the panel (expand/collaps) is also not showing up.
There is a lot of factors that can affect the appearence of a control in that time frame. Did you change your Visual Studio version while making the change? Are you using different browsers? What is aspx markup for your webpanel? As far as the images are concerned you can just do a view source on the rendered page to figure out where it is looking for the images.