No groups showing, can't perform any actions in sim?

This is driving me up the wall--my husband and I seem to swap out nights with this particular issue, has been happening for about a week.

We both have shiny new PCs, mine's HP, his is Dell, with the same graphics card (nVidia 8800GT, overclocked at the factory) and good memory (they were bought with SL-playing in mind).

We share bandwidth through a router, cable isp (and it truly is "comcastic" ...which is quite the dirty word around here).

The issue is this: Periodically on our home sim, one of us loses the ability to load the "About Land" tab. Shows as empty of all values. When we try to TP out, we get stuck in limbo and promptly crash or redmap. Groups show as "none" (but are visible in the profile, to us both when this happens) ...can't interact with anything set to group on the land, attachments won't work...

It's happened three times, fixed once on its own, a second time by restarting the sim, and is currently happening to my partner. The kicker is, this is limited to that sim--if I TP him out or he TPs me, everything works fine again.

Halp?

This cleared up on it own again, but still seeking a solution/cause if anyone has a suggestion...