Acts_as_solr throwing an Exception

Hi,

when i start the rake task for solr

like
rake solr:start
i got the following error:

** Invoke solr:start (first_time)
** Execute solr:start
Exception in thread “main” java.lang.NoClassDefFoundError:
copy/vendor/plugins/acts_as_solr/config//////////////solr/development
Caused by: java.lang.ClassNotFoundException:
copy.vendor.plugins.acts_as_solr.config…solr.development
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:319)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:264)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:332)
Could not find the main class:
copy/vendor/plugins/acts_as_solr/config/…/…/…/…//solr/development.
Program will exit.

Can anybody tell me what was the problem and how to over come.