Shares on WinXP Pro and WinXP Home

I have two PCs wirelessly networked in a workgroup in my home. One has XP Pro, and the other has XP Home. I set up shares on both PCs, and using Simple File Sharing, they both could access each other and everything was hunky-dory. I recently added a third PC with XP Home to the network, and added a shared folder on this PC. The XP Pro PC can see and access all shares on both XP Home PCs. The new XP Home PC can access all shares on both other PCs. The old XP Home PC still has access to the XP Pro PC, but cannot get access to the share on the new XP Home PC. (I get an Access Denied, check with your Sys Admin, etc, message, which is a bummer since I'm the Sys Admin). What am I doing wrong? Any help greatly appreciated.