I am currently running JDK 6 on Windows 7 and have installed the Unlimited Strength Policy Files. I wrote a Java app some time ago which used to work but now fails, giving an error message indicating that the SHA1PRNG SecureRandom is not available. I have tried printing a list of cryptographic providers available on the platform and it would appear that there are no secure random number generators available - does anyone have any idea why this might be?

Many thanks in advance for your help!