I have installed the latest WinpkFilter v3.0.4 on my Vista 32bit Business PC successfullly. But when reboot after setup, Vista is freezing and hung. So when i reboot PC on safe mode with networking, all things are ok. Meanwhile I found that on Vista Business WinpkFilter takes NDIS IM scenario, not be widely used NDIS hooking technology, why for that? My PC is equiped with intel dual core CPU along with 512M memmory and one realtek nic card.
After research of help document with WinpkFilter, NDIS hooking is also available on Vista 32bit, but only unavailable for 64bit due to OS internal protection.
In fact I have noticed that there are many existing application incompatability with Vista, so Microsoft should retract Vista development.
NDIS IM driver is a standard Windows driver and by design it has a less chance of the software conflict with other third-party applications than NDIS hooking driver. Your case looks like a software conflict.