Linework not "sticking"

[patricks]

I have a monolithic concrete stair with a concrete slab at the top. Since monolithic stairs must end with a tread, and I want my top-most tread to have the correct slanted riser, I have my slab and stair overlapping. I have used invisible linework in the plan and stair callout views to get rid of the line at the top end of the stairs, but it seems like every time I turn around, the real line is back and I have to make it invisible again. Anyone else had problems like this?

[chris.needham]

I've been having a lot of problems with linework not sticking in 2009. The biggest problem has been when I've done linework on a floor above: upon later opening of the file, the linework has disappeared.
The majority of the projects I've been working on have been migrated from 2008, so whether that has any bearing on it I don't know.