If that's the full code, then should there not be an DEFINE OSC XX to let PBP know what frequency the PIC is running at.

Have a look at my last post in this thread http://www.picbasic.co.uk/forum/showthread.php?t=20024

You may need to change the config settings to match the chip you are using, but if it has an internal 4 Mhz clock then it should work without too much modifications