normalize gives malformed url exception

[alxsss]

Hello,

I use nutch-1.6 and the following code

try{
                url = new URL(base, url);
                 imgUrl =url.toString();
                 // Normalize and Replace spaces with %20
                 url = url.replaceAll("\\s", "%20");
                 url = normalizers.normalize(url,URLNormalizers.SCOPE_FETCHER);
              }
              catch (MalformedURLException mue){
               LOG.info("MalformedURL: " + url);
               
              }

catches malformed exception for 
urls

http://mysite.com/img/banners/ads-2_50.jpg
http://mysite.com/img/writers/DWC_7996.JPG

Any ideas what might be wrong?

Thanks.
Alex.