XP networking Access denied

I have a small network of two XP professional systems
both in a workgroup. Sharing works normally.
But when I try to connect remotely through computer
management, i get the following errors:
- event viewer : "Network path not found"
- Shared folders\... : "Access denied"
- device manager : "Access denied"
- WMI control : "win32:Access is denied"
....
Both computers are in "WORKGROUP", have the same userlogin,
and the same password.
Apparently the security settings prevent me from accessing
a remote computer for anything else than file-sharing.
How can I override these settings without having a domain?

Searching in newsgroups gave me a lot of people having
similar problems, but without any answers.