New posts vanish on WP MU

Hello–

I am new here and have poked through the threads, but have not found a situation quite like mine. My programming skill is thin; please forgive my basic questions.

Here is the problem:

New posts started deleting themselves today, one day after my site was restored to correct damage I inflicted.

The troubles began when I tried to install some new plugins. I placed them in the wrong content folder — the MU content folder. This nuked all my other plugins, partially breaking the site.

(Plugin error messages: “deactivated…headers are missing.” I tried hitting “activate,” which made the plugins vanish.)

I deleted the new plugins from the MU content folder. But my other plugins did not reappear.

So my web host restored the site from a day earlier. The restored fix did not stick for very long, however. Within a few minutes my regular plugins were gone once again, along with thumbnails, calendar and other features.

A second restore seemed to bring things back to normal for about 18 hours. Users posted new entries…and then those entries disappeared.

When I tried to open these posts from their subject lines under “edit posts,” I got an error message saying there was no post, “or maybe it was deleted?”

Any ideas about where to troubleshoot would be greatly appreciated… thanks very much.