File sharing problem

I have two windows XP boxes. Computer 1 has files I want on it and a shared drive. Computer 2 has a desktop shortcut to that drive. For a long time everything was fine. I have not really accessed the shared drive on my other box in over a month. Today I was trying to use it, and I no longer can. The error I get is that I can not reach the computer or that I do not have the right permission.

From computer 2 I can not even ping computer 1, but from computer 1 I CAN ping computer 2. Both computers have full access to the internet. On computer 2, I can go to my network neighborhood and the shared drive shows up there. Clicking on it instead of the shortcut produces the same error.

The only thing I can think of is that in the last month or two I updated my Linksys Roter Bios. I have not changed any network settings on my XP boxes in a long time.

This is how my linksys is set up:
The wirless network was setup to use encryption, and not to even advertise itself. I have since stopped using the wirless half of the router since both computers are in the same room and I just ran some cables around. I would guess that the settings for these

Computer 2 is in the DMZ.

Does anyone have an idea what is wrong?

computer 2 might have windows firewall turned on. That will kill windows file sharing, pingings, etc.

Are they both running SP2? I found it nearly impossible to get a good network running between SP1 and SP2 machines.

Are they in separate IP ranges? If so, computer 2 will need a default gateway, or some sort of route to computer 1.