> How it may happen?

I don't know, I don't write the stuff. Probably just a cut-and-paste gone bad is my guess. Surely I'm not the only one who put cut-and-pasted some code, with the intention of changing the pasted text, and then forgot to change a few variable names only to spend an hour trying to figure out why my variables are getting trounced on. :-)

BTW, it's apparently been fixed in the VFP 7 help file.