*bump*
did you try disabling the stalk in the player configuration?
No, I didn't think about that, as I thought it was a hijack feature, which I don't have installed.
No, it's a standard player feature, visible in the "Configure Player" screen in emplode. It has three options: Righthand, Lefthand, and None.
So, I finally re-installed Hijack, and added the following to my config:

[controls]
stalk_side=none

To test it out, I took a three-plus hour drive up to the Kern River to go whitewater rafting. I didn't have any problems during that drive, but unfortunately, the next day while driving shuttle, I again started having the random dropping into standby. It was an intensely sunny day, so I tried to shield the IR a bit with my hand. It never dropped into standby while doing that. However, since I was driving down windy roads (i.e. I had to keep unshading to put my hand back on the wheel, not to mention watch the road), I wouldn't be able to conclusively say that it's "stray IR signals". Actually, now that I think a bit, it was happening on the drive home at night, too, so I'm ruling out the stray IR.

On the off chance that the capitalization of None matters, I've just corrected that. I'll report back again after a bit more testing.

If this still doesn't work, I think I have three options left:

0) Attempt to map all stalk input into innocuous button presses -- maybe previous/next visual.

1) Beg the Lord for a Hijack option to tell the player to ignore stalk input, whether in standby, or not. (I should be able to figure out the patch since most of this code already exists, but I don't know if my arm toolchain is currently operational for compiling/testing.)

2) Talk to pca to find out how to prevent the tuner module from sending stalk signals back to the empeg. I looked at the wiring harness details, but the tuner connecter wires were simply labelled "tuner, tuner, tuner, tuner", which, quite frankly, wasn't that helpful. (Wasn't there a thread/post about how to not wire stuff for the stalk, or was that just saying one could skip the stalk->tuner input connector?)

3) Uninstall the tuner.

I hate the thought of (3), and (2) would be a reasonable solution, if it's possible, but I'd rather not modify the tuner. My preferred solution, if this next test doesn't work, would be (1). Obviously, I'd rather not have random button presses occur, innocuous, or not, so I'd rather not go with (0).

Anyone see anything dumb in the above?