Sluggish Webrick?

Hi, I noticed recently that style sheets and javascrips in my rails
app under development does not loads properly, when I tried to access
it this is what I got:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<HTML>
  <HEAD><TITLE>Internal Server Error</TITLE></HEAD>
  <BODY>
    <H1>Internal Server Error</H1>
    private method `gsub!' called for #&lt;Class:0xb672cd18&gt;
    <HR>
    <ADDRESS>

     WEBrick/1.3.1 (Ruby/1.8.7/2010-01-10) at
     localhost:3000
    </ADDRESS>
  </BODY>
</HTML>

Any body knows whats wrong and how to fix it?