Fiber convertor not working after move

When connecting a pc directly to the fiber convertor, we have full connectivity without any dropped packets when we do a continuous ping to the other office. But, when we connect the fiber media convertor to the switch we have connectivity issues as we get only one or two replays out of every 8 to 10 pings. I have also used a cross over cable from the media convertor to the switch, but that did not help. We are using the same equipment as we did before the move and I have attached images from other setup which should help you understand our setup.  The fiver convert is a Cables to go Multimedia convertor 10/100.

Here is a more detailed description:  

We have two offices in two separate buildings. ( Main Building and small building). We had and existing setup that was working fine. After we moved around the server room in the small office we are having issue connecting to the main building.  We had fiber going in between bulding and than fiber media convertor at each end and finally the from the convertors to the switches at each end . In the main office we have two Cisco switches and at the small building we have a 16 port Dell switch.
All was working fine until we moved around the server room which required us to extend fiber cable that was coming from the fiber box (tray) to the Ethernet convertor. After we did this , I have full connectivity when I connect a pc directly to the media convertor, but I have connectivity issues when I connect the media convertor to the switch. This is the same switch that was being uses.  When pinging something on the other side out of several pings, I only get one or two replays, but the rest fail.  I also tried using another 4 port switch for testing, but I had the same results.
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Have you tried a cross over cable between the switch and the converter?

When you connect to the PC do you use auto speed and auto duplex detect, or do you hard code speed and duplex?

When connecting to the switch do you use auto/auto or fixed speed/duplex?

I would try configuring the switch port to fixed 100 Mbps full duplex and try using a cross over cable.
netcompAuthor Commented:
Yes, I have used a cross cable and it did not work.
No, I don't change anything in the pc when directly connecting it to the media convertor which works just fine.

But this is the same switch that was working for us when in the old server room. As far as which port was being used to connect the media convertor, that's something I am not sure of.  As I said above, I also tried connecting the media convertor to anthore 5 port  mini switch and dad same issue.
Is there a way you can connect a computer to the switch port and test to see what happens trying to ping it?
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netcompAuthor Commented:
As I said in my original post, I have no connectivity or ping issues when connecting a pc directly to the media convertor, but have issue when connecting the media converter to the switch.
Yes, I know.  What I'm saying is connect the PC to the switch and try and ping the PC.

that is instead of

fiber <-- converter --> copper <--> switch

PC <--> copper <--> switch
netcompAuthor Commented:
Yes, I have no issues ping the pc itself or any other computer on the same switch. It's just that we have issues when accessing other office via the fiber. We even get a DHCP address even it takes a long time, but when pinging anything on the other side, out of every 10 pings we get 3 random replays.
O.K., just to make sure I get this right:

If you do this:

   PCA <-port Y->  switch < port X--> PCB

Pings to/from PCA and PCB work fine.

If you do:

   remote site <--> fiber <-- converter --> copper <-->  PCB

Pings to the remote site from PCB or pings from the remote site toe PCB work fine.

However if you do this:

  remote site <--> fiber <-- converter --> copper <- port Y-> switch < port X--> PCB

or this:

  remote site <--> fiber <-- converter --> copper <- port X-> switch < port Y--> PCB

Ping from PCB to the remote site and ping from the remote site to PCB all have problems?

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netcompAuthor Commented:
Yes, everything pings fine locally on both sites, but all fails when pinging other site when the switch is involved.  I have tried from either site.
Now, this works fine and I can ping all.
Remote site switch --convertor---- fiber---convertor----pc

And this does not work:
remote site <--> fiber <-- converter --> copper <- port X-> switch < port Y--> PCB
netcompAuthor Commented:
Ok, I solved the issue.
It turned out that the convertor was the issue. It turned out that it was bad. I replaced it with another one and problem solved. It certainly did not look like a bad convertor as it worked with a PC directly connected to it. Thank you for you help
It is possible that the PC (and its NIC) has better auto detect that the switch and that it may have been working in half duplex to half duplex.

When there is a mismatch on duplex, you get a lot of collisions and dropped packets.
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