启动eclipse时maven插件报错，并且不能编译了。

错误信息：
Errors occurred during the build.
Error instantiating builder 'org.eclipse.m2e.core.maven2Builder'.
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Error instantiating builder 'org.eclipse.m2e.core.maven2Builder'.
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Error instantiating builder 'org.eclipse.m2e.core.maven2Builder'.
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Error instantiating builder 'org.eclipse.m2e.core.maven2Builder'.
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Error instantiating builder 'org.eclipse.m2e.core.maven2Builder'.
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Error instantiating builder 'org.eclipse.m2e.core.maven2Builder'.
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).
Plug-in org.eclipse.m2e.core was unable to load class org.eclipse.m2e.core.internal.builder.MavenBuilder.
An error occurred while automatically activating bundle org.eclipse.m2e.core (525).

求解！