I have a single, long string of engines powering to one phased pipe, or rather had. For some reason, if you have multiple PCP's set to receive from a single source, and are all on the same frequency, the connected -regular- conductive pipe directly adjacent to the -receiving- PCP will just.....POOF, disappear. Randomly, no explosions or anything so far as I've seen. It just bugs out.

Can't reproduce. Does it happen every time you make the same setup? If yes, describe/show a picture of it.

Also what versions of forge, buildcraft, and additional pipes are you using?

http://s1278.beta.photobucket.com/user/KThompson7777/media/2012-12-01_053723-edit.png.html
http://s1278.beta.photobucket.com/user/KThompson7777/media/2012-12-01_053737-edit.png.html?sort=3&o=1
In the first, circled is Send only, frequency one
It's changed, but the second would be set to frequency 1, send+receive, and the circled pipe eventually disappears.
Forge 6.4.1.407
BC a3.2.0
AP 2.1.3u28b2

LP 0.7.1-pre1 -teleport as well for main components, and
Forestry a1.6.2.0

It's a string of 31 automated peat-fire engines. Set the phase source at one end, and have multiple phase lines (a tree farm, wheat farm, carpenter, etc) eventually one of the connecting vanilla conductive pipes will disappear. I will attempt to set up a test and screenshot that as well. As shown in given screenshots, managed a workaround.

I figured it out I think. Just like with logistics pipes, when sometimes an item request can be sent to the wrong pipe because of multiple destinations creating the vanilla random destination, the power is being randomly sent to the wrong pipe, and then re-routed back to the transport phase system for its proper destination. But if the power within the pipe gets to be too much, it explodes, luckily usually only itself. Just happened again when I put my quarry on the same lines as my powered furnaces. The other furnaces were all fully powered, but I added a new one for fir logs to charcoal, and BOOM the connector pipe blew, the one directly connected to the phase pipe that is.

Yeah it's not a 'bug' so much as an inconvenience. Likewise, while I'm on a similar subject, it looks like the teleport pipes will not configure into the logistic pipe network if there are multiple destinations. For some reason, when I had my 5 wheat farms sending items to one pipe on the main network string, the logistics pipe connected to that teleport pipe showed red to all sides, but not when I switched to one pipe per farm. Bummer. I have 30+ pipes for power and items right now because of it.

So it only happens when teleport pipes are looped (one teleport pipe sends power to another, which sends it back)? If so, it's not a bug. (I remember it causing a crash in older versions, which was a bug)

Edit: I think I see the problem. I'll see if i can add more control to the teleport system.