I noticed that installing and using the latest JDK (which includes Java 7.0.1) on most computers causes JDownloader to freeze at the splash screen when launched, even if Java 6 is also present and installed properly. Suggest to either begin work on supporting Java 7.0.1 or to modify JDownloader to run on Java 6 when both versions are available and throw an error message if only Java 7 is available.

Unrelated: jdownloader.org/knowledge/bugtracker isn't properly displaying information, it just has a vague error message followed by a link to the location of a content feed.

[editestowy]

Which Java is used is determined by the system reading the PATH variable.
If Java 7 is installed after the Java 6 it may put (or even replace path to Java 6 environment) it's path at the beginning of the PATH variable. So when jDownloader is calling java executable it will use Java 7.
Start command line (CMD) and execute command:
java -version
It will tell which Java is used by the java applications.

The easiest way to use Java 6 (if there are many environments installed) is to create simple start.bat with these two commands:
set PATH="c:\Program Files\Java\jre6\bin"
jDownloader.exe

First line is the path to the default Java6 JRE environment (you must change it if your Java 6 is installed in different directory), second will start jdownloader.
It should be executed from main jD directory.

[Jiaz]

current stable works on java 1.7, but may contain some issues
to start jd, just close jd and all java processes and start jdupdate.jar
that should help.

next major release will support 1.7 officially