and Aweb
AWeb comes with ClassAct. ClassAct is the predecessor of ReAction which comes with OS 3.9. If you install ClassAct on top of OS 3.9, you downgrade ReAction to a non-supported version. That's why all OS 3.9 programs fail. It's not only string.gadget but all gadgets, images, etc. in the Classes directory.
You should copy the entire Classes directory from your OS 3.9 CD and from then on keep your fingers from ClassAct.
If you already installed a BoingBag, you might have to install it again in order to return to the latest version.