Exactly the same thing happens to me, SETIFACE.DLL at every login. This started this morning after I updated the Avast program. Also, it happens when I retry program update (even though it’s up to date now).

Win98 SE, Avast 4 home.

Write blocking is on, and I rather like the feature.
Something in Avast is trying to change the skin, isn’t it? I’ve got the blue panel skin set. Changing it to teak zeppelin, doesn’t fix the problem and causes the “The system cannot find the file specified. Cannot start incremental update.” message as well.

I’ll try Ignoring it for now, since it does seem like Avast is doing this to itself.