Microsoft Shared Fax

that's the only error ? what about the eventviewer on both machines ?
Does both machines have sp4 installed ?
Can server send a fax itself ?

awaiting your remarks,
Leopold

more info would be good. exact error. os of client the doesn't work. os of clients that DO work. service pack levels. meanwhile, maybe this'll help, i found it in knowledgebase at support.microsoft.com
--excerpt from 325807 How to set up SBS 2000 Shared Fax service---
Disable the Windows 2000 Fax Service
By default, when you install a modem in a Windows 2000-based computer, the Fax Service is enabled. The service is a core component and you cannot remove it. This client-only service is different from the SBS Shared Fax service. You must disable the Windows 2000 Fax Service. To do so:
Click Start, point to Programs, point to Administrative Tools, and then click Services.
Right-click Fax Service, and then click Properties.
Under Startup Type, click Disabled, and then click OK.

All machines are have current Service Packs. The only error i get in the eventviewer is The server was unable to allocate a work item 2 times in the last 60 seconds. I can not fax from the server. I uninstalled / reinstalled microsoft shared fax. Still no luck. starts to tranmitt and I get fatal error. When I send from the server to an outside #, it goes to the sent items, but do not receive anything on the other end. No ws work nor the server