Pic resetting

Slightly OT, but I know you guys can help on this one.

I've still been playing with this sound-2-light / chaser project but using an 16F873a. I have the patterns programme and now have a 2 x 16 LCD attached to port C (and it works !!) - however I've hit a problem with the bass beat filter.

I used an old passive filter circuit I used on a previous version, but this time used an NPN tranny to trigger a NE555. The result is fantastic and the LED on the NE555's output keeps excellent beat to the music. However, even though the PIC is not connected to the NE555, it keeps resetting itself. I can't see that the NE555 would draw so much current that it would draw the voltage down (a DVM shows the voltage around 4.6v when the LED is lit).

Could it be that the PIC needs the low voltage setting changed in some way ? Or is my filter circuit flawed ??

EDIT:
Scrub that -- fixed it with another de-coupling capacitor right near the pic's supply pins !!

Doh ! - well it was late last night and I had had a few drinks !!!

Sorry guys !

I seem to remember reading in one of my magazines many years ago that the 555 momentarily draws a lot of current from the supply when changing its output state. Try a large decoupling capacitor close to the 555 (100uF or higher)

I also seem to remember that the CMOS version 7555 is much more gentle on the power supply.

Thanks Keith, I'll give that a go too

You might also disable brown out detection on your pic config fuses too.
JS