OPiPC+ network problem solved.

After I got my OPiPC+ to finally boot without HDMI, it wouldn't boot in my shop.

I originally had it in the bedroom because that's where a convenient HDMI TV was AND that's where the U-Verse router is.

In the shop, it went through an HP Procurve 2626 switch but would hang early in the boot process.

Logged into the switch and found that most ports were set to "100FDpx".

I changed the Pi port to "Auto100" and within seconds, the Pi was booting. Yay!

Most people won't have such a problem using ordinary switches.

A year ago, I needed more ports in the shop and got a great deal on this one locally.

I didn't need 24 ports or the feature set but it was $40.00.

Turns out, some of the features have been very helpful.
An old Milan print server for my grocery list printer wouldn't work on anything but "10HDpx".