BUT BUT BUT,,,,,as pointed out earlier....Did you in code block:

if(RI)
{
}

...take care of resetting RI. This flag reqires clearing in software. Some other interrupt flags on
8051 architecture parts are set so they clear automatically when the interrupt routine is processed. The RI and TI interrupt flags for the UART however are a part of the set of interrupt flags that must be cleared by software action.

MICHAEL KARAS