eclipse adt - Working android project stopped working after updating android tools from r19 to r20 -

i came new project have been developed quite long time.

my co-workers have exact same codebase had install eclipse , adt plugin. co-workers have r19 of android tools , android platform-tools r11. i've android tools r20 , platform tools r12.

now error message after running software.

java.lang.runtimeexception: unable instantiate activity componentinfo{ com.project.package/com.project.package.myactivity}:  java.lang.classnotfoundexception:  com.project.package.myactivity in loader dalvik.system.pathclass loader 

so our manifest looks this:

<application     android:icon="@drawable/app_icon"     android:label="@string/app_name"     android:theme="@style/theme.mystyle" >     <activity         android:name=".myactivity"         android:label="@string/app_name"         android:windowsoftinputmode="adjustresize"         android:screenorientation="portrait"         android:configchanges="locale" > 

etc.

i'm using eclipse classic indigo (v. 3.8).

any idea has happened?

i had same problem after updated sdk tools r20. realised had not updated adt r20 and, once did so, problem went away.

i'm using indigo (3.7.2).