Hi Emrah Yigit,
We have a similar issue here though, reported by our QA team for the release Q1
SP1. It is related to deisgn-time only. When VS is first loaded with a form
opened in design mode that contains a RadControl, themes might not appear (do not load correctly). You can work around this issue if you close all open forms in the
design mode and restart VS 2005. Nevertheless, you should not have any problems
with themes runtime. We will fix this behavior asap. Let us know if you confirm
that you experience the same problem and if this is a show-stopper bug for you.
the Telerik team