AVR-Chat

I know this is perhaps a bit off topic but I have several boards with 
PIC16F877 processors driving an HC595 shift register and the output 
pins from the pic driving the HC595 are virtually all glitches.

It is hard to pick up a high or low as such on the logic analyser 
other outputs seem ok, has anyone any idea what may be causing this. 

And yes I do not like pic's I normally use AVR'S.

Owen.