This may not be multisite specific, but it's happening on a multisite blog, so I thought I'd post here first.
Just a few days ago I panicked when I clicked "edit" on a post and got the "error connecting to database" page. Obviously my install has had no problem accessing the database since it was set up, so I was taken aback.
I clicked "back" and tried a few more times, and after the third or fourth try it finally went to the "edit post" page. This occurs fairly consistently now.
I was very wary of what was happening, so I backed up the database just to be sure. I've contacted my host, so I'll see if it's anything technical, but I was just wondering if anyone here might have a clue what was going on. Rogue plugin, perhaps?