Mysterious switching of layers

In certain drawings, I am working on one layer, I use the fillet command or copy command, hit escape - then the drawing magically switches to another layer as current! What causes this?

Thanks

O.K. everyone, its one year later, and I'm still dealing with this issue. Let me try to explain it a little better...

Using Autocad Mechanical 2008 -

I open a drawing with layer 1 as current layer. I switch to layer 2 as current, draw some lines, fillet the lines together and quit the fillet command. As soon as I quit the fillet command, Acad switches back to layer 1 as current.

This doesn't hppen in every drawing. It is usually drawings that we receive from customers. Is there a setting to control this? If I use plain Autocad 2008 to do the work, I don't experience this issue. Could it be different reactions between standard Acad and Mechanical? Any ideas or suggestions?

Thanks,

Joe

Do you have any custom programs running within AutoCAD (stuff like .lsp / .dvb) which could cause this ?

Yes. We have quite a bit of .dvb. My colleagues don't seem to have this problem, however, and we're supposedly all configured the same.