Getting a "ClassNotFoundException" exception when running sikuli-script from command line

I have viewed few questions which seemed to have a problem similar to mine but it looks like I have something different in my case.
When I start a sikuli-script from command line under Windows 7, I get the following error:

C:\Sikuli\Tests>C:\Sikuli\sikuli-script.cmd -r C:\Sikuli\Tests\ADRS.sikuli
-Xms64M -Xmx512M -Dfile.encoding=UTF-8
-r C:\Sikuli\Tests\ADRS.sikuli
+++ using as SIKULIX_HOME: C:\Sikuli\
+++ this Sikuli version is 32-Bit
java version "1.6.0_29"
Java(TM) SE Runtime Environment (build 1.6.0_29-b11)
Java HotSpot(TM) Client VM (build 20.4-b02, mixed mode, sharing)
+++ trying to start Sikuli Script
Exception in thread "main" java.lang.NoClassDefFoundError: org/sikuli/script/Sik
uliScript
Caused by: java.lang.ClassNotFoundException: org.sikuli.script.SikuliScript
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: org.sikuli.script.SikuliScript . Program will exit.

Any suggestion as to what can cause such behavior and how can it be fixed?

Thanks in advance!