if you use a 20MHz oscillator, make sure you properly set the PIC config fuses. AT very least, osc to HS mode. There's a whole thread in the FAQ about that.

Presetting Configuration Fuses (PIC Defines) into your Program
http://www.picbasic.co.uk/forum/showthread.php?t=543

and the PicMultiCalc is available on my website

Mister E utilities page
http://www.mister-e.org/pages/utilitiespag.html