Vertices disappear?

I have a character model, and I wanted to make clothes for him. So I duplicated the model, deleted the head and limbs, and saved the file.

I alt+G to get the “shirt” back in place, tab into edit mode, and try to alt+S, but all the vertices disappear. Same thing happens if I try to edit all vertices at once (grab, scale, rotate), but it works fine when I just want to edit some vertices.

It also shows weird x,y,z positions that google helps nothing with:

http://i.imgur.com/YSON8.png

I solved it by ctrl+tabbing into edge mode, and back into vertex mode.
It still seems to be coming back at times, though.

I use ver 2.49b, btw