I tried stressing some other devices sharing IRQ 10 for testing: playing music on pcm1 while continuously rsyncing data over re0 (which is a PCIe device as well) from a memory card in a reader attached to a port whose parent is uhci0 and none of them went haywire, plus it-works-in-windows
Indeed. When the NVidia driver goes haywire my huge ethernet traffic continues just fine, so whatever the interrupt issue is, it doesn't appear to affect my ethernet. This has been true for two different ethernets, one on-board one in a PCI slot and I'm sure I re-ordered the cards so the PCI card was in a slot not shared with the NVidia (though I think the on-board wasn't either). Been too long since I looked...
And as you say "it works in windows" so it must surely be driver/FreeBSD related.
Still happy to provide NVidia with any info that would help...