EPM3128A Fitter Error after assigning a single pin

I am attempting to add 4 pins and a small amount of logic to an already existing design in my EPM3128A.

I can successfully build under the following conditions:

- Just the input pins (no assignments), additional logic and some rerouting

- Assigning 3 of the 4 input pins to the desired pins (with the above new logic and routing)

- Assigning all 4 input pins, but with the 4th assigned to a non-desired pin (with the above new logic and routing)

I can not compile when I have all of the above and assign the 4th input to pin 27 (the desired pin). I get a fitter error referring to unrelated logic (LPM_COUNTER, which is in no way connected to this new logic or pins). Compilation also fails when I assign this 4th input to pin 29, and 31. Compilation succeeds if I have this 4th input assigned to pin 24, 35, or 37. Any other nearby pins are in use already.

The hardware layout is already complete and it will be more expensive to change the pin than it would be to figure out how to compile this properly.

After searching the first error I'm getting ("Can't route source node <node> of type max_mcell to destination node <other node> of type max_mcell") I found this post (http://www.alteraforum.com/forum/showthread.php?t=28255). I get the sense I may be exceeding my macrocell count. However, with any successful compilation combination, the results are 77/128 total macrocells, and 61/80 total pins. It is the same case with any of the above successful compilations.

- Is that other post completely unrelated? It's the same error I'm getting.

- Am I just misunderstanding something?

- Is there anything I can look at or optimize to successfully compile this?

Any help is appreciated. Thanks.

- James