Cursor wrapping/unwrapping in ContentProvider

There's no need to "unwrap" the cursor. The problem is, if your content provider is providing results to a client that runs in another process, the Cursor you returned from query() must implement CrossProcessCursor interface. It's not stated in document (AFAICS), but you can see this from your log.

All you need to do is implement CrossProcessCursor interface, and wrap it around your cursor.

// your query statement does not seem right..BTW
Cursor result = mContentResolver.query(...); 
// now, you return a CrossProcessCursorWrapper.
return new CrossProcessCursorWrapper(result);

Implementation of CrossProcessCursor methods are ported from AbstractCursor. Some slight modifications are made so the compiler's happy:

public class CrossProcessCursorWrapper extends CursorWrapper implements
        CrossProcessCursor {
    public CrossProcessCursorWrapper(Cursor cursor) {
        super(cursor);
    }

    @Override
    public CursorWindow getWindow() {
        return null;
    }

    @Override
    public void fillWindow(int position, CursorWindow window) {
        if (position < 0 || position > getCount()) {
            return;
        }
        window.acquireReference();
        try {
            moveToPosition(position - 1);
            window.clear();
            window.setStartPosition(position);
            int columnNum = getColumnCount();
            window.setNumColumns(columnNum);
            while (moveToNext() && window.allocRow()) {
                for (int i = 0; i < columnNum; i++) {
                    String field = getString(i);
                    if (field != null) {
                        if (!window.putString(field, getPosition(), i)) {
                            window.freeLastRow();
                            break;
                        }
                    } else {
                        if (!window.putNull(getPosition(), i)) {
                            window.freeLastRow();
                            break;
                        }
                    }
                }
            }
        } catch (IllegalStateException e) {
            // simply ignore it
        } finally {
            window.releaseReference();
        }
    }

    @Override
    public boolean onMove(int oldPosition, int newPosition) {
        return true;
    }
}

Sounds like you use two apk's or something. You shouldn't get this with different ContentProviders using eachother within the same application. When another application tries to use your ContentProviders however you get this error. Solution is to let your custom Cursor implementation implement the CrossProcessCursor interface.