Unable to browse some Xp sp2 pc thru my network places

Hi
I am having problems with a few PCs within the domain.I can remotely connect and ping the computers but when i want to open the same pcs thru my network places,the domain open and i am able to see all the computers. but when i try to open computer “bbb” i get a message that i might not have permissions to access the network resource.Window firewll is turned off,i am using SEPM 11.0 I can browse other machines within the same domain without problems and iam defined as a domain administrator. please help!
thanks in advance.