[News.eclipse.dsdp.mtj] Unable to use night build

[fab.spinelli@xxxxxxxxx (F. Spinelli)]

Hi all. I'm an italian student trying to port an existing project based on 
Eclipse plugins onto mobile devices.
I've founded the MTJ project and downloaded the N20080430 nightly build. 
I've installed a fresh Eclipse 3.3.2 and succesfully installed the MTJ 
runtime plugins and future, but when I try to create a new "Midlet 
Project" or "Java ME Midlet" I obtain the following error messages:
1) trying to create new "Midlet Project" ---> Plugin org.eclipse.mtj.ui 
was unable ti load class 
org.eclipse.mtj.ui.internal.wizards.NewJ2MEProjectWizard
2) trying to create new "Java ME Midlet" ---> Plugin org.eclipse.mtj.ui 
was unable ti load class 
org.eclipse.mtj.ui.internal.wizards.NewMidletWizard.

It seems that some classes are not present in the downloaded plugin and 
futures.
It's a strange thing, and the two error messages seems to be "switched".

I'm also experience some trouble trying to configure preferences. If I 
open the menu Windows-->Preferences and select any of the "Mobile Tools 
for Java" preferences page I alway get this error message "Unable to 
create the selected preference page.Reason : 
org/eclipse/mtj/ui/internal/preferences/xxxPage (Unsupported major.minor 
version 49.0)" where xxx is the name of the preference page I'm trying to 
select.

I know this kind of error is related to installed and used JRE, but I'm 
using Java 6 Update 6 Sdk and properly configured preferences for compiler 
(don't know if this can help).

What's my error? Do I need to download something else? I extracted the 
jar plugins and I can't find org.eclipse.mtj.ui.internal package...

Any suggest will be very appreciate, thank you so much.

(Please, sorry for my poor English :) )