Problems with secondary MPU6050 address and compass readings

In the meantime I am able to run the MotionApps 1.1.1 UC3 Project with my eval 6050 board.
I modified the code to use also the secondary MPU6050 address (0x69). Now I found the following problem:
Once I enable the compass in the MApps 1.1.1 with the following code:

memset(&gCompass,0,sizeof(gCompass));
compass = ak8975_get_slave_descr();
memset(gPdata.compass.orientation,0,sizeof(gPdata.compass.orientation));
gPdata.compass.orientation[0] = -1;
gPdata.compass.orientation[4] = +1;
gPdata.compass.orientation[8] = -1;
gPdata.compass.adapt_num = 0;
gPdata.compass.bus = EXT_SLAVE_BUS_SECONDARY;
gPdata.compass.get_slave_descr = ak8975_get_slave_descr;
gPdata.compass.address = COMPASS_SLAVEADDR_AKM;
memcpy(&gCompass, compass, sizeof(*compass));

When I use the primary MPU6050 address (0x68) than I can read Mag values from the FIFO. But if I use the secondary address (also MPU Pin tied to high) everything is running, but I cant read any Mag values!!
What's wrong?