I tried waiting for the SSP1IF interrupt, but it never happened!
Hmm. After you initiate the START (SEN=1) and then wait for SEN to go low (SEN=0) you should be able to clear SSPIF before you write to the SSPBUF.

If you look at that figure once you write to the SSPBUF you'll see BF being asserted on the 8th clock, but SSPIF isn't asserted until the 9th after the ACK.