The mount wizard creates a JarFileSystem when verifying that a selected JAR is 
valid and not already mounted.  Even if the wizard is cancelled or another JAR 
file selected, this JarFileSystem is never disposed of, leaving the file open.  
The result is that on Windows, this file can not be deleted or moved until the 
IDE is shut down.

This is an istance of a general problem with the JFS.  It's very tempting for 
client code to create a JFS to access the jar file, or in this case have its 
system name created the canonical way.  But there's no obvious requirement to 
shut it down correctly, or even an obvious method to call to do so.