That is because either the type/creator is messed up or the resource fork is corrupted. Use the PoweBook G3 to fix it - PCs can't recognize resource forks so they often will just strip them off.
Do you have SSW 7.0.1 or higher on the Classic? I'd just have that and 6.0.8.
Do you have SSW 7.0.1 or higher on the Classic? I'd just have that and 6.0.8.