Snapping: Can't select one layer

[KatharinaDubach]

I've got a map with several shapefiles. Now I'm editing one, let's call it MyPolygons, and I want to set it to snap to the vertices of MyPolygons. But the Snapping Options dialog won't list MyPolygons. What's wrong here??

The weird thing is: I've got another layer in my TOC called Boundaries that also points to MyPolygons as its data source. I can snap to Boundaries.
Copying MyPolygons to a new mxd won't help the situation.

MyPolygons was symbolized using a .lyr-file whose source I had to adjust to make it work again. Could that be part of the problem?

I'm on ArcView 9.3 an Windows XP.

[SisiYan]

You can try exporting the shapefile out to a feature class in a geodatabase and see if the new feature class can be snapped at all.

[KatharinaDubach]

If I add the shapefile directly to ArcMap (no symbology applied), I can snap to it. But not if I use the .lyr file. Must be something wrong with that, then...