I think you have the wrong java,use this link n info to update.
Now! Go to,
START/Set Program Access/Change or Remove Programs,
now
completely remove all versions of java.
Now! Use this Link to get JRE 6 Use the off line installer NOT the (recormended) one,
http://java.sun.com/javase/downloads/index.jsp
Disconnect from internet, close ALL apps n reinstall java.
Follow thease instructions exactly.
Now you may still have to give us router brand n model but do this first
Look on the router or the box it came in and post it.
VISTA will only run on java JRE 6 at present.
Peace.