Android ClassNotFoundException with ViewPager

I am getting the following error, which I don't understand...

06-15 22:06:49.196: W/dalvikvm(17622): threadid=1: thread exiting with uncaught exception (group=0x40bcc1f8)
06-15 22:07:05.031: W/dalvikvm(17877): threadid=1: thread exiting with uncaught exception (group=0x40bcc1f8)
06-15 22:07:05.031: E/AndroidRuntime(17877): FATAL EXCEPTION: main
06-15 22:07:05.031: E/AndroidRuntime(17877): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.whipple.android/com.whipple.android.StockActivity}: android.view.InflateException: Binary XML file line #6: Error inflating class ViewPager
06-15 22:07:05.031: E/AndroidRuntime(17877):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1968)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1993)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at android.app.ActivityThread.access$600(ActivityThread.java:127)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1159)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at android.os.Handler.dispatchMessage(Handler.java:99)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at android.os.Looper.loop(Looper.java:137)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at android.app.ActivityThread.main(ActivityThread.java:4512)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at java.lang.reflect.Method.invokeNative(Native Method)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at java.lang.reflect.Method.invoke(Method.java:511)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:561)
06-15 22:07:05.031: E/AndroidRuntime(17877):    at dalvik.system.NativeStart.main(Native Method)
06-15 22:07:05.031: E/AndroidRuntime(17877): C