FILE SYSTEM WITH USB HOST FAILS WITH STM32F107

Hello I have been debugging for one week and it drives me crazy ;
I am using the file system library ; I could make it work ok with SD card but now my problem is a usb host

the only diffirent of my board from MCBSTM32C is that power control is GPIOB.15

I have changed that in the code of the MSD_file example and i can control the host power

but the problem that the software always turn back that the device is not connected .

after debugging I noticed that usbh_msc_status(0, 0) always retun false ; I am using 4GB USB flash .

my program is just to create a TXT file inside the usb flash ; I am afraid it is a library bug ; so anyone has this problem before?

Thank you in advanced

Regards
Sami