Thanks for answering..

I've trie instant interrupts but it stays the same..

I've also tried the code you wrote Skimask... the oscil. shows ~50kHz... The load you typed is too large...

Don't know what is wrong.. The oscilloscope is a Tektronix TDS2014.. it is working ok!

Anything else I can do?

Let me tell you something.. I'm using 22p capacitor at the @20Mhz... is that ok?