Can't print to networked print server on peer network

[bgalipault]

I work in a small office. We have a peer network made up of 9 Windows XP machines and one Windows XP-ME machine. All the computers belong to the same workgroup. We have a multifunction copier on the workgroup (Toshiba eStudio 3511) which also operates as an SMB-connected print server. Most of the machines on the network can print to the Toshiba, but two can't (one XP laptop and the XP-ME machine).

Our network setup: We have a broadband connection which runs through an Asante router that serves as a hardware firewall and then to a Netgear 10/100 hub. 2 other hubs are piggybacked onto the Netgear hub: a Linksys wireless and a D-Link 10/100/1000. The XP machine that is having problems is on the main Netgear hub along with the Toshiba. The XP-ME machine is on the D-Link.

Both problem machines can ping the Toshiba with no packet loss. When I click on "View Workgroup Computers", sometimes I can see the Toshiba and sometimes I can't. If I then refresh the list of workgroup computers, the Toshiba will disappear with one refresh and then reappear with another. All the unaffected machines can print to the Toshiba as well as connect to the two problem machines just fine, so we don't think the issue is faulty cables or ports. Any ideas?