Lpc2000

Has anyone had experience with their UART fifos being randomly
disabled?  For some reason, my UART0 fifo is being diabled seemingly
randomly.  The application itself is not that complex, it receives a 2
byte command and sends back 10 bytes of status.  Somehow, the fifos
get disabled, then a CTI interrupt occurs that I cannot get rid of. 
In the manual it says to clear CTI I need to read RSR.  I don't see an
RSR register, but I would assume that they meant RBR.

Any suggestions?

Thanks,
Peter