Sun Java 5.0 has been updated today to version 1.5.0_07-b03
Release notes here
You can download the updated version here
If you aren't sure which version you have then you can check your version here
It is important that old versions of Sun Java are removed
1. Close any open programs you may have running, especially your web browser.
2. Click Start > Control Panel
Depending on your OS or configuration, you may have to click Start > Settings > Control Panel
3. Open Add or Remove Programs.
If you have Windows 98 or Windows 2000, open Add/Remove Programs.
4. Click once on any item listing Java Runtime Environment in the name.
Not every version of Java will begin with "Java" so be sure to read each entry in the list.
5. Click the Remove or Change/Remove button.
6. Follow steps 4 and 5 as many times as necessary to remove all versions of Java.
7. Also, search 'Programs' and 'Application Data' and remove old version files manually. Note; Do not delete the Java VM folder if found.
C:\Program FilesC:\Documents and Settings\USERNAME\Application Data\
8. Reboot your PC once all Java components have been removed.
9. Proceed with reinstalling Java:
Continue Step 9 by going to http://java.sun.com/j2se/1.5.0/download.jsp
and install the latest version from the website.
10. Then reboot your system a final time.