Problem when downloading an applet

[oscpaz00]

Hello,

We're trying to use an applet in a page. This page is hosted in an IIS server with Windows authentication (using NTLM). When the page hosting the applet loads (in IE8) Java shows a dialog box asking for user credentials, then the .jar files are downloaded an everything works fine. But, if we try to do the same on Firefox 3.6.6, we don't see de dialog box, an the console throws an error (ClassNotFoundException) because the .jar can't be downloaded (we receive multiple 401 errors, but java doesn't show us the dialog box). We have java 1.6.0_20 installed, and we cannot understand why it works fine in IE8 and not in FireFox. I have to tell that, if I open the page in IE, and when Java asks user credentials, I check the "Remember credentials" option, then in Firefox it works fine. ¿What can we do to make this credentials dialog box appear anytime a 401 error is received?
Also, I have to mention that we are under a SOCKS proxy that also uses NTLM authentication, but, in the client network, we have also this problem in firefox (and even, somentimes, in IE).
We've tried every possible configuration and we're almost crazy with this.

Thanks for your help.

[gafa]

show us your problem code please :(

[Eranga]

Is that FF Java enable?