Tying ISSP pin to IO, setting to float, leaks voltage? errors sparatic ?

So I have a project where I have my box connected in line with two other controllers. Where module A and B used to connect directly I now have A - ME - B so I can get data in from A before B get it.

In order to save room I double functioned so of the IO wires from A to B to no only pass through my module but also splice off to be my ICSP pins. So I can use the same connector to program. As far as I know this is common.

When the code starts I set float to all the ICSP pins. The signal that is passing through is a multiplexed 5V signal (pull up and ADC in A, and resistor tree in B) But, in SOME modules I'm getting what appears to be an additional 5V source on that line. Specifically the 5V signal on PGM is getting messed up somehow. Can float get messed up with multiplexed signals and start leaking voltage? Should I set the IO registers differently? Is there a fix for this ?

Here is a diagram (kinda)
**broken link removed**

I'm using X an ADC, a b and c are my ICSP pin when plugged into my ICD2, but should just be pass through otherwise.

I've done a lot of these with no errors but all of a sudden I have multiple problems, any ideas ?

CRAP!

Someone from our wiring group just informed me that its labeled wrong. Those 5V mux signals are actually 12V. They are getting clipped to 5.75 by the internal diodes.

Well, now I'm in a mess,