Invalid JAR File Error on Samsung C3322 Duos

Hello experts,
I bought a new Samsung C3322 Duos. This is actually a good deal. The problem is, I can't seem to set up any JAR file into it. So I searched for some resolutions and found out this:
According to a forum, I need to enter *#52828378*#> Go to Menu and then change the MAX JAR file value to 2048 under the OTA. And then Save it. I tried it but it didn't work. And then later, it gives a Invalid JAR file error. Can someone please help? I also want Opera Mini on my phone. How can I put some themes into it?
