I need u r help in applets....

One of our application using the following applet type is not loading in
firefox / mozilla v1.7 browser...
But it is working fine in mozila v1.4 / firefox 3.0.6

*type ='application/x-java-applet;version=1.1.2'*

Any idea what we need to change in our code to overcome this ?
Please let me know if you need any other info