TestNG unable to find the Test class in the Classpath

The TestNg is failing to find my Test Class in the Classpath. I am attaching the MAven configuration and the TestNg.xml file.

I have tried clean up the project.This Temporarily fixes the problem.On the subsequent runs, again the same problem.

I have also tried converting the project to TestNG project in the Eclipse.This also fix the issue Temporarily.

testng.xml file

            <?xml version="1.0" encoding="UTF-8"?>
             <!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
              <suite name="Suite">
                <test thread-count="5" name="Test">
                     <classes>
                         <class name="com.yodlee.api.tests.TestAPI" />
                     </classes>
               </test> <!-- Test -->
             </suite> <!-- Suite -->

pom.xml file

                   <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.17</version>
                    <configuration>
                        <skipTests>false</skipTests>
                        <suiteXmlFiles>
                            <suiteXmlFile>testng.xml</suiteXmlFile>
                        </suiteXmlFiles>
                    </configuration>
                </plugin>