Windows Network Explorer

Hey, strange new issue:
In a network of ~10 computers, Windows suddenly stopped showing any systems in Network explorer. 'Twas working fine when I began configuring a new laptop--heck, smoother than ever before--then bam. No computer in the nework will show any of the others in its explorer window.

There's more: I worked around this, setting up shortcuts by typing in the computer and folder name. That works peachy, as do browses based on those shortcuts.

Except on one laptop which was previously fine. That one's shortcuts work sometimes, sometime don't.

Whats going on and where do I look to resolve this?

Thanks!
Ed