If you’re using the Mpowerlayer SDK for your J2ME development on Mac OS X, and you get the following ant build error:
$ ant
Buildfile: build.xml
compile:
preverify:
[exec] Error preverifying class java.lang.Class
[exec] VERIFIER ERROR java/lang/Class.newInstance0()Ljava/lang/Object;:
[exec] Illegal type in constant pool
[exec] Result: 1
package:
BUILD SUCCESSFUL
Total time: 1 second
Then you can fix it by changing the following entry in your build.xml:
<property name="java.classes.jar" value="/System/Library/Frameworks/JavaVM.framework/Classes/classes.jar" />
to
<property name="java.classes.jar" value="/System/Library/Frameworks/JavaVM.framework/Versions/1.4.2/Classes/classes.jar" />
This was the solution which i got after researching for quite sometime. However, this might have fixed issue for some, i was still facing the same issue.. 
So after debugging for some more time, realized that
/System/Library/Frameworks/JavaVM.framework/Versions/1.4.2 was a symlink to the current jdk
dv-mac-anooj-n:Versions anooj$ ls -l
total 64
lrwxr-xr-x 1 root wheel 5 Jun 26 21:09 1.3 -> 1.3.1
drwxr-xr-x 3 root wheel 102 Jul 21 2009 1.3.1
lrwxr-xr-x 1 root wheel 10 Jun 26 21:09 1.4 -> CurrentJDK
lrwxr-xr-x 1 root wheel 10 Jun 26 21:09 1.4.2 -> CurrentJDK
lrwxr-xr-x 1 root wheel 10 Jun 26 21:09 1.5 -> CurrentJDK
lrwxr-xr-x 1 root wheel 10 Jun 26 21:09 1.5.0 -> CurrentJDK
lrwxr-xr-x 1 root wheel 5 Jun 26 21:09 1.6 -> 1.6.0
drwxr-xr-x 8 root wheel 272 Jun 26 21:11 1.6.0
drwxr-xr-x 9 root wheel 306 Jun 26 21:11 A
lrwxr-xr-x 1 root wheel 1 Jun 26 21:09 Current -> A
lrwxr-xr-x 1 root wheel 3 Jun 26 21:09 CurrentJDK -> 1.6
So now i just had to remove the symlink :
sudo rm 1.4.2
and paste 1.4.2 version folder here.. Issue resolved.
PS: i got 1.4.2 from my colleagues lappy.. Donno if apple allows you to download it.
