I don't know why you've got this problem compiling. I continue suggesting go to version 4 and not staying in older 3.0 with new ide compiling is automatically
Simply :
1-download eclipse galileo
2- Intall maven plugin (m2eclipse )
3- Install svn plugin
4- checkout from svn ( not older version in cvs )
First time you need some hours to downloading all libraries needed to compile with maven, after it compilation it'll automatically for gwt and all other classes.