Successful build in Maven still showing errors in Eclipse

I'm having something quite peculiar here, my build is successful in maven when I type "mvn clean install" however once imported into Eclipse it's showing errors.

See for yourself:

I guess exluding quartz from the `pom.xml solved the problem but I'd like to know why.

PS: Here is the pom.xml in case you want to see it:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.nantes.mpclient</groupId>
  <artifactId>MyClient</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>MyClient</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>com.nantes.mp</groupId>
        <artifactId>MyEjb</artifactId>
        <version>1.0-SNAPSHOT</version>
    </dependency>
    <dependency>
        <groupId>org.jboss.jbossas</groupId>
        <artifactId>jboss-as-client</artifactId>
        <version>5.1.0.GA</version>
        <type>pom</type>
    </dependency>
  </dependencies>
</project>

###EDIT As you can see quartz is here:

Sometimes I get these types of issues as well.

Generally, what worked best for me with Eclipse & Maven:

• Use the latest m2e Eclipse plugin
• Use Maven 3
• Make sure m2e uses the same Maven version as the one you're using on the command line (not the internal one)
• Import projects as Maven projects to generate the Eclipse project files