Here is a scenario which shows the problem:

File f = new File("\\\\machine\\officebean.dll");
URL url = f.toURL();
String s = url.toString();          
URI u = new URI(s);
File f2 = new File(u);

During instantiation of f2 an IllegalArgumentException is thrown. The message is "URI has an authority component." The problem seems to be URL.toString which returns:
"file://machine/officebean.dll"
It would work if toString returned:
"file:////machine/officebean.dll"