OK. You?ve applied Service Patch 3.
Have you also checked out all the information related to the License Logging Service in Microsoft?s article Q305138, verifying and running the appropriate patch? Check the version of LLSRV.EXE and LLSRPC.DLL you are running.
Reference:
http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q305138&
If this is ok, then it?s a Client Access License (CAL) issue.
Open the Licensing Manager in the Control Panel. Is it set to ?Per Seat? or ?Per Server?? Odds are that it is set to ?Per Server?. In which case the number of licenses listed in the Licensing Manager needs to be equal to, or exceed, the number of client systems you have connecting to the server.
If it is set to ?Per Server?, you need to purchase additional Client Access Licenses to equal the number of client systems you have connecting to the server.
A temporary workaround, (until such time as you actually buy the Client Access Licenses) would be to set the server to ?Per Seat?.
A good explanation of both licensing modes is available at Microsoft.
Reference:
http://www.microsoft.com/piracy/samguide/tools/cal_guide/default.asp#seat
http://www.microsoft.com/piracy/samguide/tools/cal_guide/default.asp#server
Remember, running a network without the appropriate licenses puts you and your business at risk legally.
G'luck - Bill