cfeclipse error: Bad version number in .class file

Beware! The following method is unofficial, untested, unvalidated, and undertaken at your own risk. In any case, don't do it on a prodcution environment.

Assume the problem is as I've just described. Then a possible solution is to reconfigure Flex Builder to use a newer version of Java, for example, 1.6.0. Proceed as follows:

1) Stop Flex Builder;

2) Open the Flex Builder installation directory (usually C:\Program Files\Adobe\Flex Builder 3\). Rename the directory jre to jre_ORIGINAL;

3) Download and install the JDK of Java SE 6 Update 27 in a directory of your choice;

4) Open the installation directory of this Java installation. Copy the directory jre to the Flex Builder installation directory.

5) Start Flex Builder. It should now be running on the newer Java version. To verify, navigate as before to Help => Product Details => Configuration Details. Does this solve your original problem?

6) Should there be any critical issues, then stop Flex Builder. Delete the jre directory, and rename jre_ORIGINAL back to jre.

It is likely that your Eclipse is configured to use a version of Java that is older than the one ColdFusion uses to compile Java classes. To update Eclipse's version of Java, follow the menu

project => properties

Click on 'Java Compiler'. Choose the most recent Java compliance level (likely 1.6).