PCI USB 2.0 issue on Sawtooth G4

[monktus]

I have an old Sawtooth G4 (350 upgraded to 800, 768mb) that I recently bought a big ext USB drive for. I put a USB 2.0 card in it years ago which has been fine up until now, however the USB connection times out and the Finder crashes with this drive (WD 750GB, which is fine on my MacBook with Leopard and an old iBook with USB 2.0 and Tiger).

I've ruled out it being a problem with Tiger (fine with iBook as mentioned) and the drive works, if slowly, over the internal USB 1.1. I heard mention on Apple's discussion forums that there's an obscure problem with PCI USB 2.0 cards on G4s and I'd appreciate it if anyone has any further information on this. I've been thinking about getting a new card as I can pick up a cheap one with an NEC chipset off eBay pretty cheap (current card is ALI), and I was also considering shoehorning Leopard on to it, however I'm not convinced either would work (a Genius I know mentioned that Leopard probably wouldn't make any difference).

Long term, I'll be replacing the machine but I could do with a solution in the meantime as running the drive off USB 1.1 is a nuisance. Thanks for any suggestions.