I'm thinking about the speed of transmission as well, if it is 8MHz maybe that's too fast for the long wires and breadboards or whatever you are using.
You can lower the speed of the SPI port, I can't remember what register to write into but I'll have a look. Maybe someone else knows of the top of their head.
I thought about using transistors. 2N2222 claims to only run up to 300 mhz but I tried it anyway.
The 5490 is only rated at ~30MHz, so the transistor is 10x faster. Your problem was more likely the inversion caused by the transistor.
I read some of the library files, I can see no mention of 1GHz anywhere, can you point to the reference?. Anyway, trust us, there is no way on God's earth this sort of thing runs at that speed.
EDIT:
it'd have been showing its self when I added the first chip.
Not necessarily, more chips + more wires + more breadboards = more capacitance = slower clocks required.
You can send data once a week but if you send it too fast that can still be a problem.
Rob