MXR Blue "Sine Wave" Box... problems

[perfectsoundforever]

Hello everyone... I've built recently a Blue Box and I'm having some problems with it.  I used the Tonepad layout (http://www.tonepad.com/project.asp?id=33, if that page's working...), except for some minor changes: I used 47nF caps as C2 and C10 (instead of 50nF), a 330pf one as C3 (instead of 300pF) and 1N4148's for the diodes (though I have 1N4448 in the circuit at the moment, just changed them to check if the diodes were the problem, because I had another working BB using those diodes). I also did the 100k pot mod for the blend control and the 1 / 2 octaves switch.
The thing is... the pedal is working perfectly (or at least as "perfect" as a Blue Box can get), giving me the octave down, with the mod and blend pot doing their work. The only problem I have is a CONSTANT AND ANNOYING SOUND I CAN'T GET RID OF ANYHOW. Seriously, whenever I turn the effect on I get a constant pitch that only goes away when I start playing, only to make its comeback in every little silence between notes. I can modulate that sound, it's affected by the 1/2 octaves mod and the blend pot, as well as by the output control, so that means ...........something, I suppose. It even changes slightly its pitch if I play with the volume knob on my guitar.
I've checked the circuit all over for cold joints, shorts, wrong orientation or values of parts, I've changed both ICs several times, the transistors, and now the diodes but I couldn't get it working properly, the sound's always there. Before going crazy or smashing the board against the wall, I came here seeking for your help. Hope someone can shine some light on me, I'm obviously missing something but I can't see what.
So, here are the voltages I get with a source that reads 9.55v:
from the 4558:
1 - 4.86
2 - 5.09
3 - 2.47
4 - 0
5 - 4.64
6 - 4.46
7 - 4.66
8 - 9.65

from the CD4013
1 - 1.95
2 - 7.90
3 - 1.95
4 - 0
5 - 7.90
6 - 0
7 - 0
8 - 0
9 - 4.10
10 - 0
11 - 4.28
12 - 0
13 - 1.95
14 - 7.90

and the 2N3904's go
Q1: C - 4.30; B - 0.36; E - 0
Q2: C - 2.08; B - 0.53 (maybe 0.33, that 5 of mine looks a bit like a 3); E - 0
Q3: C - 2.10; B - 0.30; E - 0

I did an audio probe starting from the input, and as soon as I got to the 4558 the sound started again.

Hope someone can help me with this demon... otherwise I'll have to put a Tube Screamer in that pretty blue enclosure I did and just pretend... or start making drone music with annoying high frequency drones.

[perfectsoundforever]

Hello.

[Taylor]

Do you still hear the oscillation when the blend is all the way on the effected side?

[perfectsoundforever]

I do. It makes a change though, not in pitch (as in a glissando) but like it should do with the guitar signal, I hear it one octave higher or lower depending on the blend pot setting. Obviously, this noise must be generated before the octave efect, because I can change it as well with the mod's SPDT.
The only thing I can add for now is that I tried a CD4558 I had lying around and it behaved in a different way now... I couldn't hear the constant pitch anymore, but an interminent and rythmic noise (like I was touching the copper side of the board), and when I played, it was like the signal of my guitar couldn't really get through, sounding like a glitchy tremolo with the same rythm as the background noise. Which probably doesn't mean anything to you, but well, just in case!

[perfectsoundforever]

I noticed something today... the sound is not in the background, but it's like the pedal was receiving that signal... When I play really softly or let the notes fade out, the guitar and the sound make all sorts of glissandos, generating just one note between them. Like they were fighting to take over the resulting pitch.