[QUOTE=flotulopex;30449]I'll try with a 4MHz crystal.

Check the datasheet for the 16F88, page 100. You are using a 4mhz at 9600 baud. If you do the math, just like the datasheet says, you'll be 6.99% off at 9600 baud using the regular 'lo-speed' baud rate generator. Switch over to the high speed baud rate generator and you'll only be .16% off at 9600. Either that or switch down to 2400 baud and see what happens (.17% error at that speed with the lo-speed baud rate generator).
If the 2400 works with lo-speed, do like I said (switch to the hi-speed BRG) and see what happens..