Lpc2000

Hi LPC group,

I have an unnice problem regarding the LPC 214x USB communication:

I've built a project based on the Keil MassStorage example.
The only difference: I changed the descriptor to a non-class device, 
setup 7in/7out pipes (I only use 2 BULK_IN and 1 BULK_OUT, needed 
this amount of declared pipes for descriptor compatibility reasons).
I've also added 1 timer interrupt, and 2 UART interrupts.

1 BULK_IN and 1 BULK_OUT are used as command bulk pipes which are 
used handshaked (means every command written is answered).

In application level (non-interrupt driven, called by main loop) I 
check if I received some data e.g. over UART. The UART is buffered by 
a ringbuffer (ISR -> ringbuffer) and the application sends the 
received data from ringbuffer->USB (calling USB_WriteEP()).

Now the problem: This works OK for several hours, but then mostly in 
WrCmd() after writing CMD_CODE the while-loop waiting for CCEMTY_INT 
doesn't leave, resulting in a hanging USB communication.

I've seen a hanging situation also in the USB ISR after setting 
EP_INT_CLR and waiting for CDFULL_INT.

I tried to disable the USB interrupt while calling USB_WriteEP() - 
same result (may be a bit better, but can't say exactly).
I also tried to send only within an USB interrupt (SOF irq), same 
result too.

So my questions:
- Does anybody else have this problem ?
- What can be the reason for a non-accepted CMD_CODE or a
  non-accepted write to EP_INT_CLR ?
- What to I need to take care of before calling USB_WriteEP() ?
- Is it forbidden to send by application level ?
- Is there a patch for the Keil USB stack ?
- Is there some errata about this ?
- What can I do to prevent this or what to resolve this situation ?

Thank you for your help

Gregor