Doing the following seems to handle overruns:
; if nothing received, check for FIFO overrun
peeksfr RCSTA,b0 ; look at OERR bit
if bit1 <> 1 then fifook
peeksfr RCREG,b6 ; read the FIFO twice, then...
peeksfr RCREG,b6
hsersetup B300_4, 0 ; redo hsersetup to clear the error
fifook: