From Forum Nokia Wiki

Carbide.j was Nokia's IDE for Java ME. Nokia discontinued it in 2007. This note explains why:

When Nokia first introduced the Nokia Developer’s Suite for J2ME™, the forerunner of Carbide.j, the support for mobile development provided by most Java™ IDEs was limited. However, over the past couple of years, features specifically aimed at mobile developers have become increasingly common in a range of open source and free Java development solutions. Therefore, having reviewed the options available to mobile Java developers, Nokia has decided not to develop Carbide.j further.

So instead of using Carbide.j, use either NetBeans or Eclipse and the EclipseME plugin to develop. See articles Java ME and Getting started with Java ME.

For those who still have a previous Carbide.j licence you can download the original version which does not have support and will NOT install on Windows Vista due to the age of the install kit and will NOT be fixed. This kit is only recommended for people who have previously used this product as there is no support for it. An outdated installation guide is available here, and a datasheet here. Many known problems exist for this product.