This forum section is for problems and questions concerning the Visual Style Builder itself. In this case the problem is probably not related to the VSB tool.
Please check how many CSS files you have on the page and make sure they are not more than 31, as IE is unable to handle them.
Also, validate the HTML and CSS code and make sure there are no syntax (parse) errors, which could lead to the browser ignoring most of the CSS rules.
Finally, make sure that the CSS fules are actually served to the browser.
If the problem persists, we will need a live URL or some runnable standalone sample to inspect.
the Telerik team