Hi Mark
Try this first & get back
Now! Go to,
START/Set Program Access/Change or Remove Programs,
now completely remove all versions of java.
Re BOOT Your computer NOW.
Now! Use this Link to get (jre-1.5.11) Use the off line installer, NOT the (recommended) one,
Java SE Downloads - Previous Release - JDK 5
When Download is completed.
Disconnect from internet, close ALL apps n reinstall java.