Can anyone explain what's just happened to my grid???

I have a very very simple grid with 8 columns. I don't set the recordsource of the grid or the control source of each column until I need to...with the following code:

IF USED("alsItem") THEN
USE IN alsItem
ENDIF

USE lv_ClinicItem IN 0 ALIAS alsItem EXCLUSIVE

thisform.grdItem.RecordSource="alsItem"

Thisform.grdItem.grcItemNo.ControlSource="alsItem.cl_itemno"
Thisform.grdItem.grcDate.ControlSource="alsItem.cl_date"
etc...

This has been working quite happily until an hour an a half ago when it decided to go bonkers. Specifically it started giving errors that the columns did not exist.

We checked that the recordsource of the grid and controlsource of each column were blank and they were. We tried using a new grid...that didn't work. We checked that using a different view or table worked...they worked. We re-created the view....that didn't work.

I've gone to my backup from lunchtime now, but I'd love to know (or have some idea at least) what caused this for future reference.

Pablo