Remote Desktop Does Not Work Within Home Network

Hello, nice to meet you all.

I have a home network with a Linksys Boradband Router WRT54G. I have 3 PCs in my home within my network. It seems i can't remote connect from any of the wireless PCs to my main one where the router is connected to (the one with my local non-wireless connection) . I get no error messages. I simply click CONNECT and it comes back IMMEDIATELY to the "connect" screen.

For example, i launch Remote Desktop from a wireless PC, input the IP of the main local PC and click "Connect", but it keeps coming back immediately to the very same screen, as if nothing ever happened.

This wasn't a problem in the past. One day i reimaged my OS and suddenly it's never worked again. I later decided to do a clean install of Windows, and still have the same problem.

I wonder if there's a setting in my router OR deep within Windows im missing?

I already checked some of the obvious settings such as allowing access to Remote Desktop through my router, windows firewall, enabling incomng connections via the "Remote tab" under Control Panel, etc.

I have:
Win XP SP3, Intel Core Quad 2.8, 4 GB RAM.

Any suggestions? Thanks!