Compile / run problems with netbeans 6 but not netbeans 6 beta 1 or 5.5

Question

When I compile my project in netbeans IDE 6.0 (Build 200711261600) 1.6.0_01; Java HotSpot(TM) Client VM 1.6.0_01-b06 i get quite often a "can not find symbol" error or during runtime a "netbeans 6 java.lang.NoClassDefFoundError" exception. also switching between F6 or ctrl-F5 mode can cause the problem to appear.
Compiling again or clean build resolves it.
However running the same project under netbeans 5.5 or 6 beta 1 never gives this problem.
any hint what might be wrong? i looked and compared the project settings but can't see any difference, but I assume that the upgrade script must have changed something.

Answer 1

<?xml version="1.0" encoding="UTF-8" ?>
- <project name="BorderDemo" default="default" basedir=".">
<import file="nbproject/build-impl.xml" />
</project>This is 'build.xml' file. Check for 'project.xml' file in 'nbproject' folder. You will find it to be:
<?xml version="1.0" encoding="UTF-8" ?>
- <project xmlns="http://www.netbeans.org/ns/project/1">
  <type>org.netbeans.modules.java.j2seproject</type>
- <configuration>
- <data xmlns="http://www.netbeans.org/ns/j2se-project/3">
  <name>BorderDemo</name>
  <minimum-ant-version>1.6.5</minimum-ant-version>
- <source-roots>
  <root id="src.dir" />
  </source-roots>
  </data>
  </configuration>
  </project>Change it to:
<?xml version="1.0" encoding="UTF-8" ?>
- <project xmlns="http://www.netbeans.org/ns/project/1">
  <type>org.netbeans.modules.java.j2seproject</type>
- <configuration>
- <data xmlns="http://www.netbeans.org/ns/j2se-project/3">
  <name>BorderDemo</name>
  <minimum-ant-version>1.6.5</minimum-ant-version>
- <source-roots>
  <root id="src.dir" />
  </source-roots>
  <test-roots>
  <root id="test.src.dir" />
  </test-roots>
  </data>
  </configuration>
  </project>I hope it works.....
thanks!