I upgraded maven 2.0.4 to 2.0.7 and the i couldn't compile the existing projects because of filtering problem - filtering files couldn't be read, the source of problem was maven-assembly-plugin. I think such kind of incongruities generally may occur. The simplest solution of such problems is simply renaming the maven folder ...\.m2\repository\org\apache\ and installing the project again for full download of all maven and maven plugins :)
The details of the problem and the solution is below:
http://jira.codehaus.org/browse/MASSEMBLY-178
