Errors in Bamboo build after upgrading from Clover 2.4.0 to 2.5.1

One of my modules with (luckily) only a few unit tests started giving this error on every unit test:

java.lang.NoSuchFieldError: E
at com.vcommerce.storefront.rightnow.RightNowLocatorTester.setUp(RightNowLocatorTester.java:19)

The line number appears to always be the Junit setUp() method.

In addition, two unit tests in the same test case throw this:

java.lang.NoSuchMethodError: com_cenqua_clover.CoverageRecorder.globalSliceStart(Ljava/lang/Class;I)V
at com.vcommerce.storefront.integrations.webloyalty.WLEncryptionTester.testEncryption(WLEncryptionTester.java:20)

I can't find any differences between this module's build.xml and the other 10 that work fine. The only modification I've made to the build.xml along with the upgrade was to add:

<taskdef resource="cloverjunitlib.xml" classpath="${clover.jar}"/>

... as recommended for Ant 1.7.