Rubicon, Have you tried using the SERIN2 command instead of the SERIN? I have used the SERIN2/SEROUT2 commands in the past with 16F84's with no problem. For 300 baud true logic the mode number would be 3313 and for 300 baud inverted logic the mode number would be 19697. I also beleive the SERIN2/SEROUT2 commands give you more options as far as data handling.

HTH,
Dave Purola,N8NTA