Import error from Eclipse with *.jar

my error log :

 12-17 18:04:36.774: W/dalvikvm(25806): Link of class 'Lcom/xxx/login/xxxLoginActivity$1;' failed
 12-17 18:04:36.774: E/dalvikvm(25806): Could not find class 'com.xxx.login.xxxLoginActivity$1', referenced from method com.xxx.login.xxxLoginActivity.<init>
 12-17 18:04:36.774: W/dalvikvm(25806): VFY: unable to resolve new-instance 1522 (Lcom/xxx/login/xxxLoginActivity$1;) in Lcom/xxx/login/xxxLoginActivity;
 12-17 18:04:36.784: W/dalvikvm(25806): VFY: unable to find class referenced in signature (Lcom/chartboost/sdk/ChartboostDelegate;)
 

issue describe:

When I use a third-party jar it will be crashed. For example, I use:

 > Class aClass = Class.forName("com.xxx.login.xxxLoginActivity");

And in fact this com.xxx.login.xxxLoginActivity exist in my jar inside.

I also found similar problems on other website, he also uses the unity.But his problem has not been resolved.See this url:link text