PvuII cuts 5'CAG/CTG3' whereas SalI cuts 5'G/TCGAC3'. Even though sequences look similar they are different in orientation. As these enzymes are very sequence specific (including sequence orientation), there is no way PvuIII cuts a SalI site and vice versa.
I would like to up vote the answer of Dominique Liger. the recognition site of both these enzymes in question are reverse of each other. One should keep in mind that the recognition sequence would also be reverse in the complementary strand.
So the answer is 'PvuII can not digest at SalI enzyme site'. and if your experience is otherwise, check for contamination...