Snap to Arrowhead on Dimension entities

In some of my drawings, I can snap to the endpoints and midpoints of dimension entities like arrowheads, extension and dimension lines, etc. Also to the insertion points of the dim text.

Usually (like 95%) I can't.

I figure there's some type of enviornment setting, but I have not been able to find it.

These are fully asssociative dims in AutoCAD Mechanical 2005, but they carry this over and act the same way when opened in AutoCAD 2008 as well.

Anyone know why this happens 5% of the time and how to eliminate this?

In some of my drawings, I can snap to the endpoints and midpoints of dimension entities like arrowheads, extension and dimension lines, etc. Also to the insertion points of the dim text.

 

Usually (like 95%) I can't.

 

I figure there's some type of enviornment setting, but I have not been able to find it.

 

These are fully asssociative dims in AutoCAD Mechanical 2005, but they carry this over and act the same way when opened in AutoCAD 2008 as well.

 

Anyone know why this happens 5% of the time and how to eliminate this?

In Mech 2008 go to Options, AM Preferences, snap defaults, filter options (lower left), check the ones you want to snap to. Or use command AMPOWERSNAP, filter options, check the ones you want to snap to.

I don't know why, but that worked.

Thanks.