Weirder issues ... resolved

Yes, you have experienced what is known in the field as "air gap
attenuation"--not something you want to depend on if you want a clean
link! A close relative is "knot-in-the-fiber attenuation".

Your subject says "GigE Media converter" but you say you are deploying
an OC12. Which is it?

Apologies. An OC12 was layed down, and I was running the drops from
building to building. This is the exact deal of what happened (now that I
can sit down for moment and think on a level head):

I was setting up the fiber lines (multi mode already layed down) to
connect the media converters to my switches. There are altogether about 8
buildings but for clarity I'll focus on the three which the event

Building A - Main point
Building B - about 1200 feet from Building A
Building C - about 600 feet from Building A

In Building A, I hooked up my media converter (Netgear) to Building B.
Light was on, I had a signal going out. Walked over to Building B to hook
up that media converter (Netgear) and this oddity occurred - link droppage
when SC connector was fully plugged.

Walked back over to Building A to replicate the incident, meaning I fully
plugged Building B and wanted to see if I slightly pulled out Building A's
SC if it would drop link. Sure enough it did.

Now back in Building A, I took off Building C's media converter (Netgear)
and swapped it with Building C which worked fine. Building C took Building
B's media converter and pushed light with no problem.

Now Building C is ALMOST twice as far as Building B is so if attenuation
was the case, when I swapped out the media converters it should have done
the same thing. Weirder was, everthing worked except I could not open the
browser interface for the switches. At first I thought it was a VLAN issue
so I walked back to the main building and added a port to have
connectivity to every VLAN on the switch. Didn't work.

So... One funky connection for a moment: Linked, pings out everywhere,
could ssh everywhere, could do anything BUT open a browser throughout the
entire Building B. Just bizarre.

Definitely invest in a light meter that can do the usual flavors
of single and multimode, connector types, and at least 850 and 1310nm
wavelengths. Then simply test strength of light on your receive port
on each side, compare to specifications of your equipment, and add
in-line attenuators as necessary. You'll usually find a range something
like -3 to -27 dBm, and we prefer -15 dBm as our ideal. Also, make
sure you've got the right type of fiber jumpers--mixing up single
(yellow) and multi (orange) mode fiber can cause similar issues.

All in all it's up now. After playing switcharoonee with these silly
little Netgears, they seemed to bork themselves into working.

Thanks to all of the responses from everyone.