2924 SFP Basic Connectivity Problem

[kurasoe]

Hello.

I have a 3COM 2924-SFP but I am having an issue.

Scenario 1 Works:

Workstation -> Small Patch Cable -> 3COM 2924-SFP Port -> Small Patch Cable -> Mobile Broadband Router

In this scenario I have the 2924 and the router on my desk.  Everything is configured/working just fine.  This seems to rule out an issue with the switch (maybe) and the router or PC (definitely) or given cabling.

Scenario 2 Works:

Workstation -> Small Patch Cable -> Outlet Punchdown -> 200' of Cat5E -> Mobile Broadband Router

In this scenario I'm using what will be the typical setup (the 200' of wiring to my wiring closet), except that I am not using the 2924 device.  I'm plugging directly into my internet access device at the other end.  Works fine.  This seems to rule out this 200' of cabling.

Scenario 3 Does Not Work:

Workstation -> Small Patch Cable -> Outlet Punchdown -> 200' of Cat5E -> 3COM 2924-SFP Port -> Mobile Broadband Router

This does not work.

So, with everything close by, it works.  This seems to rule out the switch and router and given patch cables.  This is scenario 1.

With the "normal" long wire run setup and no 2924, it works.  This seems to rule out the 200' ethernet line.  Scenario 2.

With the "normal" long wire run and the 2924 in place, nothing works.  Scenario 3.  Windows says a network cable is unplugged.  However it seems the 2924, router, patch cabling, and 200' line have all been proven out through scenarios 1 and 2, right?

The only common thing here is the long 200' run WITH the 2924 in place.  Long cable, no 2924, internet accessed.  No long cable, 2924 in place, internet accessed.  Long cable, 2924 in place, no connectivity.

Help!